Ziele Untersuchung
mit Columbo Integrität von
Datenbanken Interaktion und
Portierbarkeit Ergonomie der
Schnittstellen

Angebot Produkte Projekt Beratung

Mittel Analytik Modellierung Sprachen Algebra Logik Hardware Denken Kreativität

Zusammenhänge Gesellschaft Wirtschaft Branche Firma


products/Sources/formale Sprachen/Java/Openjdk/test/jdk/java/lang/invoke/ (Sun/Oracle ^©) Datei vom 13.11.2022 mit Größe 41 kB

Quelle JavaDocExamplesTest.java Sprache: JAVA

/*
* Copyright (c) 2009, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

/* @test
* @summary example code used in javadoc for java.lang.invoke API
* @compile JavaDocExamplesTest.java
* @run testng/othervm test.java.lang.invoke.JavaDocExamplesTest
*/

package test.java.lang.invoke;

import java.io.StringWriter;
import java.lang.invoke.*;
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;

import java.util.*;

import org.testng.*;
import org.testng.annotations.*;

/**
* @author jrose
*/
public class JavaDocExamplesTest {
    /** Wrapper for running the TestNG tests in this module.
     *  Put TestNG on the classpath!
     */
    public static void main(String... ignore) throws Throwable {
        new JavaDocExamplesTest().run();
    }

    public void run() throws Throwable {
        testMisc();
        testFindStatic();
        testFindConstructor();
        testFindVirtual();
        testFindSpecial();
        testPermuteArguments();
        testZero();
        testDropArguments();
        testDropArgumentsToMatch();
        testFilterArguments();
        testFoldArguments();
        testFoldArguments2();
        testMethodHandlesSummary();
        testAsSpreader();
        testAsCollector();
        testAsVarargsCollector();
        testAsFixedArity();
        testAsTypeCornerCases();
        testMutableCallSite();
    }
    // How much output?
    static final Class<?> THIS_CLASS = JavaDocExamplesTest.class;
    static int verbosity = Integer.getInteger(THIS_CLASS.getSimpleName()+".verbosity", 0);

{}
private static final Lookup LOOKUP = lookup();
// static final private MethodHandle CONCAT_1 = LOOKUP.findVirtual(String.class,
//     "concat", methodType(String.class, String.class));
// static final private MethodHandle HASHCODE_1 = LOOKUP.findVirtual(Object.class,
//     "hashCode", methodType(int.class));

// form required if ReflectiveOperationException is intercepted:
    private static final MethodHandle CONCAT_2, HASHCODE_2, ADD_2, SUB_2;
static {
  try {
    Class<?> THIS_CLASS = LOOKUP.lookupClass();
    CONCAT_2 = LOOKUP.findVirtual(String.class,
      "concat", methodType(String.class, String.class));
    HASHCODE_2 = LOOKUP.findVirtual(Object.class,
      "hashCode", methodType(int.class));
    ADD_2 = LOOKUP.findStatic(THIS_CLASS, "add", methodType(int.class, int.class, int.class));
    SUB_2 = LOOKUP.findStatic(THIS_CLASS, "sub", methodType(int.class, int.class, int.class));
   } catch (ReflectiveOperationException ex) {
     throw new RuntimeException(ex);
   }
}
    static int add(int x, int y) { return x + y; }
    static int sub(int x, int y) { return x - y; }

{}

    @Test public void testMisc() throws Throwable {
// Extra tests, not from javadoc:
{}
MethodHandle CONCAT_3 = LOOKUP.findVirtual(String.class,
  "concat", methodType(String.class, String.class));
MethodHandle HASHCODE_3 = LOOKUP.findVirtual(Object.class,
  "hashCode", methodType(int.class));
//assertEquals("xy", (String) CONCAT_1.invokeExact("x", "y"));
assertEquals("xy", (String) CONCAT_2.invokeExact("x", "y"));
assertEquals("xy", (String) CONCAT_3.invokeExact("x", "y"));
//assertEquals("xy".hashCode(), (int) HASHCODE_1.invokeExact((Object)"xy"));
assertEquals("xy".hashCode(), (int) HASHCODE_2.invokeExact((Object)"xy"));
assertEquals("xy".hashCode(), (int) HASHCODE_3.invokeExact((Object)"xy"));
{}
    }

    @Test public void testFindStatic() throws Throwable {
{}
MethodHandle MH_asList = publicLookup().findStatic(Arrays.class,
  "asList", methodType(List.class, Object[].class));
assertEquals("[x, y]", MH_asList.invoke("x", "y").toString());
{}
    }

    @Test public void testFindVirtual() throws Throwable {
{}
MethodHandle MH_concat = publicLookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
MethodHandle MH_hashCode = publicLookup().findVirtual(Object.class,
  "hashCode", methodType(int.class));
MethodHandle MH_hashCode_String = publicLookup().findVirtual(String.class,
  "hashCode", methodType(int.class));
assertEquals("xy", (String) MH_concat.invokeExact("x", "y"));
assertEquals("xy".hashCode(), (int) MH_hashCode.invokeExact((Object)"xy"));
assertEquals("xy".hashCode(), (int) MH_hashCode_String.invokeExact("xy"));
// interface method:
MethodHandle MH_subSequence = publicLookup().findVirtual(CharSequence.class,
  "subSequence", methodType(CharSequence.class, int.class, int.class));
assertEquals("def", MH_subSequence.invoke("abcdefghi", 3, 6).toString());
// constructor "internal method" must be accessed differently:
MethodType MT_newString = methodType(void.class); //()V for new String()
try { assertEquals("impossible", lookup()
        .findVirtual(String.class, "", MT_newString));
} catch (NoSuchMethodException ex) { } // OK
MethodHandle MH_newString = publicLookup()
  .findConstructor(String.class, MT_newString);
assertEquals("", (String) MH_newString.invokeExact());
{}
    }

    @Test public void testFindConstructor() throws Throwable {
{}
MethodHandle MH_newArrayList = publicLookup().findConstructor(
  ArrayList.class, methodType(void.class, Collection.class));
Collection orig = Arrays.asList("x", "y");
Collection copy = (ArrayList) MH_newArrayList.invokeExact(orig);
assert(orig != copy);
assertEquals(orig, copy);
// a variable-arity constructor:
MethodHandle MH_newProcessBuilder = publicLookup().findConstructor(
  ProcessBuilder.class, methodType(void.class, String[].class));
ProcessBuilder pb = (ProcessBuilder)
  MH_newProcessBuilder.invoke("x", "y", "z");
assertEquals("[x, y, z]", pb.command().toString());
{}
    }

// for testFindSpecial
{}
static class Listie extends ArrayList {
  public String toString() { return "[wee Listie]"; }
  static Lookup lookup() { return MethodHandles.lookup(); }
}
{}

    @Test public void testFindSpecial() throws Throwable {
{}
// no access to constructor via invokeSpecial:
MethodHandle MH_newListie = Listie.lookup()
  .findConstructor(Listie.class, methodType(void.class));
Listie l = (Listie) MH_newListie.invokeExact();
try { assertEquals("impossible", Listie.lookup().findSpecial(
        Listie.class, "", methodType(void.class), Listie.class));
} catch (NoSuchMethodException ex) { } // OK
// access to super and self methods via invokeSpecial:
MethodHandle MH_super = Listie.lookup().findSpecial(
  ArrayList.class, "toString" , methodType(String.class), Listie.class);
MethodHandle MH_this = Listie.lookup().findSpecial(
  Listie.class, "toString" , methodType(String.class), Listie.class);
MethodHandle MH_duper = Listie.lookup().findSpecial(
  Object.class, "toString" , methodType(String.class), Listie.class);
assertEquals("[]", (String) MH_super.invokeExact(l));
assertEquals(""+l, (String) MH_this.invokeExact(l));
assertEquals("[]", (String) MH_duper.invokeExact(l)); // ArrayList method
try { assertEquals("inaccessible", Listie.lookup().findSpecial(
        String.class, "toString", methodType(String.class), Listie.class));
} catch (IllegalAccessException ex) { } // OK
Listie subl = new Listie() { public String toString() { return "[subclass]"; } };
assertEquals(""+l, (String) MH_this.invokeExact(subl)); // Listie method
{}
    }

    @Test public void testPermuteArguments() throws Throwable {
        {{
{} /// JAVADOC
MethodType intfn1 = methodType(int.class, int.class);
MethodType intfn2 = methodType(int.class, int.class, int.class);
MethodHandle sub = SUB_2;// ... {int x, int y => x-y} ...;
assert(sub.type().equals(intfn2));
MethodHandle sub1 = permuteArguments(sub, intfn2, 0, 1);
MethodHandle rsub = permuteArguments(sub, intfn2, 1, 0);
assert((int)rsub.invokeExact(1, 100) == 99);
MethodHandle add = ADD_2;// ... {int x, int y => x+y} ...;
assert(add.type().equals(intfn2));
MethodHandle twice = permuteArguments(add, intfn1, 0, 0);
assert(twice.type().equals(intfn1));
assert((int)twice.invokeExact(21) == 42);
            }}
        {{
{} /// JAVADOC
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodHandle d0 = dropArguments(cat, 0, String.class);
assertEquals("yz", (String) d0.invokeExact("x", "y", "z"));
MethodHandle d1 = dropArguments(cat, 1, String.class);
assertEquals("xz", (String) d1.invokeExact("x", "y", "z"));
MethodHandle d2 = dropArguments(cat, 2, String.class);
assertEquals("xy", (String) d2.invokeExact("x", "y", "z"));
MethodHandle d12 = dropArguments(cat, 1, int.class, boolean.class);
assertEquals("xz", (String) d12.invokeExact("x", 12, true, "z"));
            }}
    }

@Test public void testZero() throws Throwable {
        {{
{} /// JAVADOC
Class<?> type = Double.class;
MethodHandle mh1 = MethodHandles.explicitCastArguments(MethodHandles.constant(Object.class, null), methodType(type));
assertEquals("()Double", mh1.type().toString());
MethodHandle mh2 = MethodHandles.empty(methodType(type));
assertEquals("()Double", mh2.type().toString());
        }}
   }

    @Test public void testDropArguments() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class);
MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2));
assertEquals(bigType, d0.type());
assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z"));
            }}
        {{
{} /// JAVADOC
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodHandle d0 = dropArguments(cat, 0, String.class);
assertEquals("yz", (String) d0.invokeExact("x", "y", "z"));
MethodHandle d1 = dropArguments(cat, 1, String.class);
assertEquals("xz", (String) d1.invokeExact("x", "y", "z"));
MethodHandle d2 = dropArguments(cat, 2, String.class);
assertEquals("xy", (String) d2.invokeExact("x", "y", "z"));
MethodHandle d12 = dropArguments(cat, 1, int.class, boolean.class);
assertEquals("xz", (String) d12.invokeExact("x", 12, true, "z"));
            }}
    }

    @Test public void testDropArgumentsToMatch() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle h0= constant(boolean.class, true);
MethodHandle h1 = lookup().findVirtual(String.class, "concat", methodType(String.class, String.class));
MethodType bigType = h1.type().insertParameterTypes(1, String.class, int.class);
MethodHandle h2 = dropArguments(h1, 0, bigType.parameterList());
if (h1.type().parameterCount() < h2.type().parameterCount()) {
    h1 = dropArgumentsToMatch(h1, 0, h2.type().parameterList(), 0);  // lengthen h1
}
else {
    h2 = dropArgumentsToMatch(h2, 0, h1.type().parameterList(), 0);    // lengthen h2
}
MethodHandle h3 = guardWithTest(h0, h1, h2);
assertEquals("xy", h3.invoke("x", "y", 1, "a", "b", "c"));
        }}
    }

    @Test public void testFilterArguments() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
MethodHandle upcase = lookup().findVirtual(String.class,
  "toUpperCase", methodType(String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodHandle f0 = filterArguments(cat, 0, upcase);
assertEquals("Xy", (String) f0.invokeExact("x", "y")); // Xy
MethodHandle f1 = filterArguments(cat, 1, upcase);
assertEquals("xY", (String) f1.invokeExact("x", "y")); // xY
MethodHandle f2 = filterArguments(cat, 0, upcase, upcase);
assertEquals("XY", (String) f2.invokeExact("x", "y")); // XY
            }}
    }

    @Test public void testCollectArguments() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle deepToString = publicLookup()
  .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
MethodHandle ts1 = deepToString.asCollector(String[].class, 1);
assertEquals("[strange]", (String) ts1.invokeExact("strange"));
MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
assertEquals("[up, down]", (String) ts2.invokeExact("up", "down"));
MethodHandle ts3 = deepToString.asCollector(String[].class, 3);
MethodHandle ts3_ts2 = collectArguments(ts3, 1, ts2);
assertEquals("[top, [up, down], strange]",
             (String) ts3_ts2.invokeExact("top", "up", "down", "strange"));
MethodHandle ts3_ts2_ts1 = collectArguments(ts3_ts2, 3, ts1);
assertEquals("[top, [up, down], [strange]]",
             (String) ts3_ts2_ts1.invokeExact("top", "up", "down", "strange"));
MethodHandle ts3_ts2_ts3 = collectArguments(ts3_ts2, 1, ts3);
assertEquals("[top, [[up, down, strange], charm], bottom]",
             (String) ts3_ts2_ts3.invokeExact("top", "up", "down", "strange", "charm", "bottom"));
            }}
    }

    @Test public void testFoldArguments() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class,
  "println", methodType(void.class, String.class))
    .bindTo(System.out);
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
assertEquals("boojum", (String) cat.invokeExact("boo", "jum"));
MethodHandle catTrace = foldArguments(cat, trace);
// also prints "boo":
assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
            }}
    }

    static void assertEquals(Object exp, Object act) {
        if (verbosity > 0)
            System.out.println("result: "+act);
        Assert.assertEquals(exp, act);
    }

    static void assertTrue(boolean b) {
        if (verbosity > 0) {
            System.out.println("result: " + b);
        }
        Assert.assertTrue(b);
    }

    @Test public void testMethodHandlesSummary() throws Throwable {
        {{
{} /// JAVADOC
Object x, y; String s; int i;
MethodType mt; MethodHandle mh;
MethodHandles.Lookup lookup = MethodHandles.lookup();
// mt is (char,char)String
mt = MethodType.methodType(String.class, char.class, char.class);
mh = lookup.findVirtual(String.class, "replace", mt);
s = (String) mh.invokeExact("daddy",'d','n');
// invokeExact(Ljava/lang/String;CC)Ljava/lang/String;
assertEquals(s, "nanny");
// weakly typed invocation (using MHs.invoke)
s = (String) mh.invokeWithArguments("sappy", 'p', 'v');
assertEquals(s, "savvy");
// mt is (Object[])List
mt = MethodType.methodType(java.util.List.class, Object[].class);
mh = lookup.findStatic(java.util.Arrays.class, "asList", mt);
assert(mh.isVarargsCollector());
x = mh.invoke("one", "two");
// invoke(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/Object;
assertEquals(x, java.util.Arrays.asList("one","two"));
// mt is (Object,Object,Object)Object
mt = MethodType.genericMethodType(3);
mh = mh.asType(mt);
x = mh.invokeExact((Object)1, (Object)2, (Object)3);
// invokeExact(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
assertEquals(x, java.util.Arrays.asList(1,2,3));
// mt is ()int
mt = MethodType.methodType(int.class);
mh = lookup.findVirtual(java.util.List.class, "size", mt);
i = (int) mh.invokeExact(java.util.Arrays.asList(1,2,3));
// invokeExact(Ljava/util/List;)I
assert(i == 3);
mt = MethodType.methodType(void.class, String.class);
mh = lookup.findVirtual(java.io.PrintStream.class, "println", mt);
mh.invokeExact(System.out, "Hello, world.");
// invokeExact(Ljava/io/PrintStream;Ljava/lang/String;)V
{}
            }}
    }

    @Test public void testAsSpreader() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle equals = publicLookup()
  .findVirtual(String.class, "equals", methodType(boolean.class, Object.class));
assert( (boolean) equals.invokeExact("me", (Object)"me"));
assert(!(boolean) equals.invokeExact("me", (Object)"thee"));
// spread both arguments from a 2-array:
MethodHandle eq2 = equals.asSpreader(Object[].class, 2);
assert( (boolean) eq2.invokeExact(new Object[]{ "me", "me" }));
assert(!(boolean) eq2.invokeExact(new Object[]{ "me", "thee" }));
// try to spread from anything but a 2-array:
for (int n = 0; n <= 10; n++) {
  Object[] badArityArgs = (n == 2 ? new Object[0] : new Object[n]);
  try { assert((boolean) eq2.invokeExact(badArityArgs) && false); }
  catch (IllegalArgumentException ex) { } // OK
}
// spread both arguments from a String array:
MethodHandle eq2s = equals.asSpreader(String[].class, 2);
assert( (boolean) eq2s.invokeExact(new String[]{ "me", "me" }));
assert(!(boolean) eq2s.invokeExact(new String[]{ "me", "thee" }));
// spread second arguments from a 1-array:
MethodHandle eq1 = equals.asSpreader(Object[].class, 1);
assert( (boolean) eq1.invokeExact("me", new Object[]{ "me" }));
assert(!(boolean) eq1.invokeExact("me", new Object[]{ "thee" }));
// spread no arguments from a 0-array or null:
MethodHandle eq0 = equals.asSpreader(Object[].class, 0);
assert( (boolean) eq0.invokeExact("me", (Object)"me", new Object[0]));
assert(!(boolean) eq0.invokeExact("me", (Object)"thee", (Object[])null));
// asSpreader and asCollector are approximate inverses:
for (int n = 0; n <= 2; n++) {
    for (Class<?> a : new Class<?>[]{Object[].class, String[].class, CharSequence[].class}) {
        MethodHandle equals2 = equals.asSpreader(a, n).asCollector(a, n);
        assert( (boolean) equals2.invokeWithArguments("me", "me"));
        assert(!(boolean) equals2.invokeWithArguments("me", "thee"));
    }
}
MethodHandle caToString = publicLookup()
  .findStatic(Arrays.class, "toString", methodType(String.class, char[].class));
assertEquals("[A, B, C]", (String) caToString.invokeExact("ABC".toCharArray()));
MethodHandle caString3 = caToString.asCollector(char[].class, 3);
assertEquals("[A, B, C]", (String) caString3.invokeExact('A', 'B', 'C'));
MethodHandle caToString2 = caString3.asSpreader(char[].class, 2);
assertEquals("[A, B, C]", (String) caToString2.invokeExact('A', "BC".toCharArray()));
            }}
    }

    @Test public void testAsCollector() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle deepToString = publicLookup()
  .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
assertEquals("[won]",   (String) deepToString.invokeExact(new Object[]{"won"}));
MethodHandle ts1 = deepToString.asCollector(Object[].class, 1);
assertEquals(methodType(String.class, Object.class), ts1.type());
//assertEquals("[won]", (String) ts1.invokeExact(         new Object[]{"won"})); //FAIL
assertEquals("[[won]]", (String) ts1.invokeExact((Object) new Object[]{"won"}));
// arrayType can be a subtype of Object[]
MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
assertEquals(methodType(String.class, String.class, String.class), ts2.type());
assertEquals("[two, too]", (String) ts2.invokeExact("two", "too"));
MethodHandle ts0 = deepToString.asCollector(Object[].class, 0);
assertEquals("[]", (String) ts0.invokeExact());
// collectors can be nested, Lisp-style
MethodHandle ts22 = deepToString.asCollector(Object[].class, 3).asCollector(String[].class, 2);
assertEquals("[A, B, [C, D]]", ((String) ts22.invokeExact((Object)'A', (Object)"B", "C", "D")));
// arrayType can be any primitive array type
MethodHandle bytesToString = publicLookup()
  .findStatic(Arrays.class, "toString", methodType(String.class, byte[].class))
  .asCollector(byte[].class, 3);
assertEquals("[1, 2, 3]", (String) bytesToString.invokeExact((byte)1, (byte)2, (byte)3));
MethodHandle longsToString = publicLookup()
  .findStatic(Arrays.class, "toString", methodType(String.class, long[].class))
  .asCollector(long[].class, 1);
assertEquals("[123]", (String) longsToString.invokeExact((long)123));
            }}
    }

    @SuppressWarnings("rawtypes")
    @Test public void testAsVarargsCollector() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle deepToString = publicLookup()
  .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
MethodHandle ts1 = deepToString.asVarargsCollector(Object[].class);
assertEquals("[won]",   (String) ts1.invokeExact(    new Object[]{"won"}));
assertEquals("[won]",   (String) ts1.invoke(         new Object[]{"won"}));
assertEquals("[won]",   (String) ts1.invoke(                      "won" ));
assertEquals("[[won]]", (String) ts1.invoke((Object) new Object[]{"won"}));
// findStatic of Arrays.asList(...) produces a variable arity method handle:
MethodHandle asList = publicLookup()
  .findStatic(Arrays.class, "asList", methodType(List.class, Object[].class));
assertEquals(methodType(List.class, Object[].class), asList.type());
assert(asList.isVarargsCollector());
assertEquals("[]", asList.invoke().toString());
assertEquals("[1]", asList.invoke(1).toString());
assertEquals("[two, too]", asList.invoke("two", "too").toString());
String[] argv = { "three", "thee", "tee" };
assertEquals("[three, thee, tee]", asList.invoke(argv).toString());
assertEquals("[three, thee, tee]", asList.invoke((Object[])argv).toString());
List ls = (List) asList.invoke((Object)argv);
assertEquals(1, ls.size());
assertEquals("[three, thee, tee]", Arrays.toString((Object[])ls.get(0)));
            }}
    }

    @Test public void testAsFixedArity() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle asListVar = publicLookup()
  .findStatic(Arrays.class, "asList", methodType(List.class, Object[].class))
  .asVarargsCollector(Object[].class);
MethodHandle asListFix = asListVar.asFixedArity();
assertEquals("[1]", asListVar.invoke(1).toString());
Exception caught = null;
try { asListFix.invoke((Object)1); }
catch (Exception ex) { caught = ex; }
assert(caught instanceof ClassCastException);
assertEquals("[two, too]", asListVar.invoke("two", "too").toString());
try { asListFix.invoke("two", "too"); }
catch (Exception ex) { caught = ex; }
assert(caught instanceof WrongMethodTypeException);
Object[] argv = { "three", "thee", "tee" };
assertEquals("[three, thee, tee]", asListVar.invoke(argv).toString());
assertEquals("[three, thee, tee]", asListFix.invoke(argv).toString());
assertEquals(1, ((List) asListVar.invoke((Object)argv)).size());
assertEquals("[three, thee, tee]", asListFix.invoke((Object)argv).toString());
            }}
    }

    @Test public void testAsTypeCornerCases() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle i2s = publicLookup()
  .findVirtual(Integer.class, "toString", methodType(String.class));
i2s = i2s.asType(i2s.type().unwrap());
MethodHandle l2s = publicLookup()
  .findVirtual(Long.class, "toString", methodType(String.class));
l2s = l2s.asType(l2s.type().unwrap());

Exception caught = null;
try { i2s.asType(methodType(String.class, String.class)); }
catch (Exception ex) { caught = ex; }
assert(caught instanceof WrongMethodTypeException);

i2s.asType(methodType(String.class, byte.class));
i2s.asType(methodType(String.class, Byte.class));
i2s.asType(methodType(String.class, Character.class));
i2s.asType(methodType(String.class, Integer.class));
l2s.asType(methodType(String.class, byte.class));
l2s.asType(methodType(String.class, Byte.class));
l2s.asType(methodType(String.class, Character.class));
l2s.asType(methodType(String.class, Integer.class));
l2s.asType(methodType(String.class, Long.class));

caught = null;
try { i2s.asType(methodType(String.class, Long.class)); }
catch (Exception ex) { caught = ex; }
assert(caught instanceof WrongMethodTypeException);

MethodHandle i2sGen = i2s.asType(methodType(String.class, Object.class));
MethodHandle l2sGen = l2s.asType(methodType(String.class, Object.class));

i2sGen.invoke(42);  // int -> Integer -> Object -> Integer -> int
i2sGen.invoke((byte)4);  // byte -> Byte -> Object -> Byte -> byte -> int
l2sGen.invoke(42);  // int -> Integer -> Object -> Integer -> int
l2sGen.invoke((byte)4);  // byte -> Byte -> Object -> Byte -> byte -> int
l2sGen.invoke(0x420000000L);

caught = null;
try { i2sGen.invoke(0x420000000L); } // long -> Long -> Object -> Integer CCE
catch (Exception ex) { caught = ex; }
assert(caught instanceof ClassCastException);

caught = null;
try { i2sGen.invoke("asdf"); } // String -> Object -> Integer CCE
catch (Exception ex) { caught = ex; }
assert(caught instanceof ClassCastException);
{}
            }}
    }

    @Test public void testMutableCallSite() throws Throwable {
        {{
{} /// JAVADOC
MutableCallSite name = new MutableCallSite(MethodType.methodType(String.class));
MethodHandle MH_name = name.dynamicInvoker();
MethodType MT_str1 = MethodType.methodType(String.class);
MethodHandle MH_upcase = MethodHandles.lookup()
    .findVirtual(String.class, "toUpperCase", MT_str1);
MethodHandle worker1 = MethodHandles.filterReturnValue(MH_name, MH_upcase);
name.setTarget(MethodHandles.constant(String.class, "Rocky"));
assertEquals("ROCKY", (String) worker1.invokeExact());
name.setTarget(MethodHandles.constant(String.class, "Fred"));
assertEquals("FRED", (String) worker1.invokeExact());
// (mutation can be continued indefinitely)
/*
* </pre></blockquote>
* <p>
* The same call site may be used in several places at once.
* <blockquote><pre>
*/
MethodType MT_str2 = MethodType.methodType(String.class, String.class);
MethodHandle MH_cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
MethodHandle MH_dear = MethodHandles.insertArguments(MH_cat, 1, ", dear?");
MethodHandle worker2 = MethodHandles.filterReturnValue(MH_name, MH_dear);
assertEquals("Fred, dear?", (String) worker2.invokeExact());
name.setTarget(MethodHandles.constant(String.class, "Wilma"));
assertEquals("WILMA", (String) worker1.invokeExact());
assertEquals("Wilma, dear?", (String) worker2.invokeExact());
{}
            }}
    }

    @Test public void testSwitchPoint() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle MH_strcat = MethodHandles.lookup()
    .findVirtual(String.class, "concat", MethodType.methodType(String.class, String.class));
SwitchPoint spt = new SwitchPoint();
assert(!spt.hasBeenInvalidated());
// the following steps may be repeated to re-use the same switch point:
MethodHandle worker1 = MH_strcat;
MethodHandle worker2 = MethodHandles.permuteArguments(MH_strcat, MH_strcat.type(), 1, 0);
MethodHandle worker = spt.guardWithTest(worker1, worker2);
assertEquals("method", (String) worker.invokeExact("met", "hod"));
SwitchPoint.invalidateAll(new SwitchPoint[]{ spt });
assert(spt.hasBeenInvalidated());
assertEquals("hodmet", (String) worker.invokeExact("met", "hod"));
{}
            }}
    }

    @Test public void testFoldArguments2() throws Throwable {
        {{
{} /// JAVADOC
// argument-based dispatch for methods of the form boolean x.___(y: String)
Lookup lookup = publicLookup();
// first, a tracing hack:
MethodHandle println = lookup.findVirtual(java.io.PrintStream.class, "println", methodType(void.class, String.class));
MethodHandle arrayToString = lookup.findStatic(Arrays.class, "toString", methodType(String.class, Object[].class));
MethodHandle concat = lookup.findVirtual(String.class, "concat", methodType(String.class, String.class));
MethodHandle arrayToString_DIS = filterReturnValue(arrayToString, concat.bindTo("DIS:"));
MethodHandle arrayToString_INV = filterReturnValue(arrayToString, concat.bindTo("INV:"));
MethodHandle printArgs_DIS = filterReturnValue(arrayToString_DIS, println.bindTo(System.out)).asVarargsCollector(Object[].class);
MethodHandle printArgs_INV = filterReturnValue(arrayToString_INV, println.bindTo(System.out)).asVarargsCollector(Object[].class);
// metaobject protocol:
MethodType mtype = methodType(boolean.class, String.class);
MethodHandle findVirtual = lookup.findVirtual(Lookup.class,
  "findVirtual", methodType(MethodHandle.class, Class.class, String.class, MethodType.class));
MethodHandle getClass = lookup.findVirtual(Object.class,
  "getClass", methodType(Class.class));
MethodHandle dispatch = findVirtual;
dispatch = filterArguments(dispatch, 1, getClass);
dispatch = insertArguments(dispatch, 3, mtype);
dispatch = dispatch.bindTo(lookup);
assertEquals(methodType(MethodHandle.class, Object.class, String.class), dispatch.type());
MethodHandle invoker = invoker(mtype.insertParameterTypes(0, Object.class));
// wrap tracing around the dispatch and invoke steps:
dispatch = foldArguments(dispatch, printArgs_DIS.asType(dispatch.type().changeReturnType(void.class)));
invoker = foldArguments(invoker, printArgs_INV.asType(invoker.type().changeReturnType(void.class)));
invoker = dropArguments(invoker, 2, String.class);  // ignore selector
// compose the dispatcher and the invoker:
MethodHandle invokeDispatched = foldArguments(invoker, dispatch);
Object x = "football", y = new java.util.Scanner("bar");
assert( (boolean) invokeDispatched.invokeExact(x, "startsWith", "foo"));
assert(!(boolean) invokeDispatched.invokeExact(x, "startsWith", "#"));
assert( (boolean) invokeDispatched.invokeExact(x, "endsWith", "all"));
assert(!(boolean) invokeDispatched.invokeExact(x, "endsWith", "foo"));
assert( (boolean) invokeDispatched.invokeExact(y, "hasNext", "[abc]+[rst]"));
assert(!(boolean) invokeDispatched.invokeExact(y, "hasNext", "[123]+[789]"));
            }}
    }

    static int one(int k) { return 1; }
    static int inc(int i, int acc, int k) { return i + 1; }
    static int mult(int i, int acc, int k) { return i * acc; }
    static boolean pred(int i, int acc, int k) { return i < k; }
    static int fin(int i, int acc, int k) { return acc; }

    @Test public void testLoop() throws Throwable {
        MethodHandle MH_inc, MH_one, MH_mult, MH_pred, MH_fin;
        Class<?> I = int.class;
        MH_inc = LOOKUP.findStatic(THIS_CLASS, "inc", methodType(I, I, I, I));
        MH_one = LOOKUP.findStatic(THIS_CLASS, "one", methodType(I, I));
        MH_mult = LOOKUP.findStatic(THIS_CLASS, "mult", methodType(I, I, I, I));
        MH_pred = LOOKUP.findStatic(THIS_CLASS, "pred", methodType(boolean.class, I, I, I));
        MH_fin = LOOKUP.findStatic(THIS_CLASS, "fin", methodType(I, I, I, I));
        {{
{} /// JAVADOC
// iterative implementation of the factorial function as a loop handle
// null initializer for counter, should initialize to 0
MethodHandle[] counterClause = new MethodHandle[]{null, MH_inc};
MethodHandle[] accumulatorClause = new MethodHandle[]{MH_one, MH_mult, MH_pred, MH_fin};
MethodHandle loop = MethodHandles.loop(counterClause, accumulatorClause);
assertEquals(120, loop.invoke(5));
{}
        }}
    }

    static int inc(int i) { return i + 1; } // drop acc, k
    static int mult(int i, int acc) { return i * acc; } //drop k
    static boolean cmp(int i, int k) { return i < k; }

    @Test public void testSimplerLoop() throws Throwable {
        MethodHandle MH_inc, MH_mult, MH_cmp;
        Class<?> I = int.class;
        MH_inc = LOOKUP.findStatic(THIS_CLASS, "inc", methodType(I, I));
        MH_mult = LOOKUP.findStatic(THIS_CLASS, "mult", methodType(I, I, I));
        MH_cmp = LOOKUP.findStatic(THIS_CLASS, "cmp", methodType(boolean.class, I, I));
        {{
{} /// JAVADOC
// simplified implementation of the factorial function as a loop handle
// null initializer for counter, should initialize to 0
MethodHandle MH_one = MethodHandles.constant(int.class, 1);
MethodHandle MH_pred = MethodHandles.dropArguments(MH_cmp, 1, int.class); // drop acc
MethodHandle MH_fin = MethodHandles.dropArguments(MethodHandles.identity(int.class), 0, int.class); // drop i
MethodHandle[] counterClause = new MethodHandle[]{null, MH_inc};
MethodHandle[] accumulatorClause = new MethodHandle[]{MH_one, MH_mult, MH_pred, MH_fin};
MethodHandle loop = MethodHandles.loop(counterClause, accumulatorClause);
assertEquals(720, loop.invoke(6));
{}
        }}
    }

    // for testFacLoop
{}
static class FacLoop {
  final int k;
  FacLoop(int k) { this.k = k; }
  int inc(int i) { return i + 1; }
  int mult(int i, int acc) { return i * acc; }
  boolean pred(int i) { return i < k; }
  int fin(int i, int acc) { return acc; }
}
{}

    // assume MH_inc, MH_mult, and MH_pred are handles to the above methods
    @Test public void testFacLoop() throws Throwable {
        MethodHandle MH_FacLoop, MH_inc, MH_mult, MH_pred, MH_fin;
        Class<?> I = int.class;
        MH_FacLoop = LOOKUP.findConstructor(FacLoop.class, methodType(void.class, I));
        MH_inc = LOOKUP.findVirtual(FacLoop.class, "inc", methodType(I, I));
        MH_mult = LOOKUP.findVirtual(FacLoop.class, "mult", methodType(I, I, I));
        MH_pred = LOOKUP.findVirtual(FacLoop.class, "pred", methodType(boolean.class, I));
        MH_fin = LOOKUP.findVirtual(FacLoop.class, "fin", methodType(I, I, I));
        {{
{} /// JAVADOC
// instance-based implementation of the factorial function as a loop handle
// null initializer for counter, should initialize to 0
MethodHandle MH_one = MethodHandles.constant(int.class, 1);
MethodHandle[] instanceClause = new MethodHandle[]{MH_FacLoop};
MethodHandle[] counterClause = new MethodHandle[]{null, MH_inc};
MethodHandle[] accumulatorClause = new MethodHandle[]{MH_one, MH_mult, MH_pred, MH_fin};
MethodHandle loop = MethodHandles.loop(instanceClause, counterClause, accumulatorClause);
assertEquals(5040, loop.invoke(7));
{}
        }}
    }

    static List<String> initZip(Iterator<String> a, Iterator<String> b) { return new ArrayList<>(); }
    static boolean zipPred(List<String> zip, Iterator<String> a, Iterator<String> b) { return a.hasNext() && b.hasNext(); }
    static List<String> zipStep(List<String> zip, Iterator<String> a, Iterator<String> b) {
        zip.add(a.next());
        zip.add(b.next());
        return zip;
    }

    @Test public void testWhileLoop() throws Throwable {
        MethodHandle MH_initZip, MH_zipPred, MH_zipStep;
        Class<?> IT = Iterator.class;
        Class<?> L = List.class;
        MH_initZip = LOOKUP.findStatic(THIS_CLASS, "initZip", methodType(L, IT, IT));
        MH_zipPred = LOOKUP.findStatic(THIS_CLASS, "zipPred", methodType(boolean.class, L, IT, IT));
        MH_zipStep = LOOKUP.findStatic(THIS_CLASS, "zipStep", methodType(L, L, IT, IT));
        {{
{} /// JAVADOC
// implement the zip function for lists as a loop handle
MethodHandle loop = MethodHandles.whileLoop(MH_initZip, MH_zipPred, MH_zipStep);
List<String> a = Arrays.asList("a", "b", "c", "d");
List<String> b = Arrays.asList("e", "f", "g", "h");
List<String> zipped = Arrays.asList("a", "e", "b", "f", "c", "g", "d", "h");
assertEquals(zipped, (List<String>) loop.invoke(a.iterator(), b.iterator()));
{}
        }}
    }

    static int zero(int limit) { return 0; }
    static int step(int i, int limit) { return i + 1; }
    static boolean pred(int i, int limit) { return i < limit; }

    @Test public void testDoWhileLoop() throws Throwable {
        MethodHandle MH_zero, MH_step, MH_pred;
        Class<?> I = int.class;
        MH_zero = LOOKUP.findStatic(THIS_CLASS, "zero", methodType(I, I));
        MH_step = LOOKUP.findStatic(THIS_CLASS, "step", methodType(I, I, I));
        MH_pred = LOOKUP.findStatic(THIS_CLASS, "pred", methodType(boolean.class, I, I));
        {{
{} /// JAVADOC
// int i = 0; while (i < limit) { ++i; } return i; => limit
MethodHandle loop = MethodHandles.doWhileLoop(MH_zero, MH_step, MH_pred);
assertEquals(23, loop.invoke(23));
{}
        }}
    }

    static String step(String v, int counter, String start_) { return "na " + v; }  //#0
    static String step(String v, int counter ) { return "na " + v; } //#1
    static String step(String v, int counter, int iterations_, String pre, String start_) { return pre + " " + v; } //#2
    static String step3(String v, int counter, String pre) { return pre + " " + v; } //#3

    @Test public void testCountedLoop() throws Throwable {
        MethodHandle MH_step;
        Class<?> S = String.class, I = int.class;
        // Theme:
        MH_step = LOOKUP.findStatic(THIS_CLASS, "step", methodType(S, S, I, S));
        {{
{} /// JAVADOC
// String s = "Lambdaman!"; for (int i = 0; i < 13; ++i) { s = "na " + s; } return s;
// => a variation on a well known theme
MethodHandle fit13 = MethodHandles.constant(int.class, 13);
MethodHandle start = MethodHandles.identity(String.class);
MethodHandle loop = MethodHandles.countedLoop(fit13, start, MH_step);  // (v, i, _) -> "na " + v
assertEquals("na na na na na na na na na na na na na Lambdaman!", loop.invoke("Lambdaman!"));
{}
        }}
        // Variation #1:
        MH_step = LOOKUP.findStatic(THIS_CLASS, "step", methodType(S, S, I));
        {{
{} /// JAVADOC
// String s = "Lambdaman!"; for (int i = 0; i < 13; ++i) { s = "na " + s; } return s;
// => a variation on a well known theme
MethodHandle count = MethodHandles.dropArguments(MethodHandles.identity(int.class), 1, String.class);
MethodHandle start = MethodHandles.dropArguments(MethodHandles.identity(String.class), 0, int.class);
MethodHandle loop = MethodHandles.countedLoop(count, start, MH_step);  // (v, i) -> "na " + v
assertEquals("na na na na na na na na na na na na na Lambdaman!", loop.invoke(13, "Lambdaman!"));
{}
            assertEquals("na na Lambdaman!", loop.invoke(2, "Lambdaman!"));
            assertEquals("Lambdaman!", loop.invoke(0, "Lambdaman!"));
            assertEquals("Lambdaman!", loop.invoke(-1, "Lambdaman!"));
            assertEquals("Lambdaman!", loop.invoke(Integer.MIN_VALUE, "Lambdaman!"));
        }}
        // Variation #2:
        MH_step = LOOKUP.findStatic(THIS_CLASS, "step", methodType(S, S, I, I, S, S));
        {{
{} /// JAVADOC
// String s = "Lambdaman!", t = "na"; for (int i = 0; i < 13; ++i) { s = t + " " + s; } return s;
// => a variation on a well known theme
MethodHandle count = MethodHandles.identity(int.class);
MethodHandle start = MethodHandles.dropArguments(MethodHandles.identity(String.class), 0, int.class, String.class);
MethodHandle loop = MethodHandles.countedLoop(count, start, MH_step);  // (v, i, _, pre, _) -> pre + " " + v
assertEquals("na na na na na na na na na na na na na Lambdaman!", loop.invoke(13, "na", "Lambdaman!"));
{}
        }}
        // Variation #3:
        MH_step = LOOKUP.findStatic(THIS_CLASS, "step3", methodType(S, S, I, S));
        {{
{} /// JAVADOC
// String s = "Lambdaman!", t = "na"; for (int i = 0; i < 13; ++i) { s = t + " " + s; } return s;
// => a variation on a well known theme
MethodType loopType = methodType(String.class, String.class, int.class, String.class);
MethodHandle count = MethodHandles.dropArgumentsToMatch(MethodHandles.identity(int.class),    0, loopType.parameterList(), 1);
MethodHandle start = MethodHandles.dropArgumentsToMatch(MethodHandles.identity(String.class), 0, loopType.parameterList(), 2);
MethodHandle body  = MethodHandles.dropArgumentsToMatch(MH_step,                              2, loopType.parameterList(), 0);
MethodHandle loop = MethodHandles.countedLoop(count, start, body);  // (v, i, pre, _, _) -> pre + " " + v
assertEquals("na na na na na na na na na na na na na Lambdaman!", loop.invoke("na", 13, "Lambdaman!"));
{}
        }}
    }

    static List<String> reverseStep(List<String> r, String e) {
        r.add(0, e);
        return r;
    }
    static List<String> newArrayList() { return new ArrayList<>(); }

    @Test public void testIteratedLoop() throws Throwable {
        MethodHandle MH_newArrayList, MH_reverseStep;
        Class<?> L = List.class, S = String.class;
        MH_newArrayList = LOOKUP.findStatic(THIS_CLASS, "newArrayList", methodType(L));
        MH_reverseStep = LOOKUP.findStatic(THIS_CLASS, "reverseStep", methodType(L, L, S));
        {{
{} /// JAVADOC
// reverse a list
MethodHandle loop = MethodHandles.iteratedLoop(null, MH_newArrayList, MH_reverseStep);
List<String> list = Arrays.asList("a", "b", "c", "d", "e");
List<String> reversedList = Arrays.asList("e", "d", "c", "b", "a");
assertEquals(reversedList, (List<String>) loop.invoke(list));
{}
        }}
    }

    @Test public void testFoldArguments3() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class,
        "println", methodType(void.class, String.class))
        .bindTo(System.out);
MethodHandle cat = lookup().findVirtual(String.class,
        "concat", methodType(String.class, String.class));
assertEquals("boojum", (String) cat.invokeExact("boo", "jum"));
MethodHandle catTrace = foldArguments(cat, 1, trace);
// also prints "jum":
assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
{}
        }}
    }

    @Test public void testAsCollector2() throws Throwable {
        {{
{} /// JAVADOC
StringWriter swr = new StringWriter();
MethodHandle swWrite = LOOKUP.findVirtual(StringWriter.class, "write", methodType(void.class, char[].class, int.class, int.class)).bindTo(swr);
MethodHandle swWrite4 = swWrite.asCollector(0, char[].class, 4);
swWrite4.invoke('A', 'B', 'C', 'D', 1, 2);
assertEquals("BC", swr.toString());
swWrite4.invoke('P', 'Q', 'R', 'S', 0, 4);
assertEquals("BCPQRS", swr.toString());
swWrite4.invoke('W', 'X', 'Y', 'Z', 3, 1);
assertEquals("BCPQRSZ", swr.toString());
{}
        }}
    }

    @Test public void testAsSpreader2() throws Throwable {
        {{
{} /// JAVADOC
MethodHandle compare = LOOKUP.findStatic(Objects.class, "compare", methodType(int.class, Object.class, Object.class, Comparator.class));
MethodHandle compare2FromArray = compare.asSpreader(0, Object[].class, 2);
Object[] ints = new Object[]{3, 9, 7, 7};
Comparator<Integer> cmp = (a, b) -> a - b;
assertTrue((int) compare2FromArray.invoke(Arrays.copyOfRange(ints, 0, 2), cmp) < 0);
assertTrue((int) compare2FromArray.invoke(Arrays.copyOfRange(ints, 1, 3), cmp) > 0);
assertTrue((int) compare2FromArray.invoke(Arrays.copyOfRange(ints, 2, 4), cmp) == 0);
{}
        }}
    }

    /* ---- TEMPLATE ----
    @Test public void testFoo() throws Throwable {
        {{
{} /// JAVADOC
{}
            }}
    }
    */
}

quality86%

¤ Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.0.23Bemerkung: (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.