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Java example source code file (MethodReferenceTestMethodHandle.java)

This example Java source code file (MethodReferenceTestMethodHandle.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

additf, arraylist, character, formatitf, integer, methodhandle, methodreferencetestmethodhandle, methodtype, object, one, replaceitf, testing, throwable, util

The MethodReferenceTestMethodHandle.java Java example source code

/*
 * Copyright (c) 2013, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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
 * @bug 8028739
 * @summary javac generates incorrect descriptor for MethodHandle::invoke
 * @run testng MethodReferenceTestMethodHandle
 */

import java.lang.invoke.*;
import java.util.*;

import org.testng.annotations.Test;
import static org.testng.Assert.assertEquals;

@Test
public class MethodReferenceTestMethodHandle {

  MethodHandles.Lookup lookup = MethodHandles.lookup();

  interface ReplaceItf {
      Object apply(String a, char b, char c) throws Throwable;
  }

  interface FormatItf {
      Object apply(String a, Object... args) throws Throwable;
  }

  interface AddItf {
      void apply(List st, int idx, Object v) throws Throwable;
  }

  public void testVirtual() throws Throwable {

      MethodType mt = MethodType.methodType(String.class, char.class, char.class);
      MethodHandle ms = lookup.findVirtual(String.class, "replace", mt);

      // --- String.replace(String, char, char) ---

      assertEquals("oome otring to oearch", ms.invoke("some string to search", 's', 'o'));

      ReplaceItf f1 = (a, b, c) -> ms.invoke(a,b,c);
      assertEquals("oome otring to oearch", f1.apply("some string to search", 's', 'o'));

      ReplaceItf f2 = ms::invoke;
      assertEquals("oome otring to oearch", f2.apply("some string to search", 's', 'o'));
      assertEquals("oome otring to oearch", f2.apply("some string to search", new Character('s'), 'o'));
      assertEquals("oome otring to oearch", ((ReplaceItf) ms::invoke).apply("some string to search", 's', 'o'));
  }

  public void testStatic() throws Throwable {
      MethodType fmt = MethodType.methodType(String.class, String.class, (new Object[1]).getClass());
      MethodHandle fms = lookup.findStatic(String.class, "format", fmt);

      // --- String.format(String, Object...) ---

      assertEquals("Testing One 2 3", fms.invoke("Testing %s %d %x", "One", new Integer(2), 3));

      FormatItf ff2 = fms::invoke;
      assertEquals("Testing One 2 3", ff2.apply("Testing %s %d %x", "One", new Integer(2), 3));
      assertEquals("Testing One 2 3", ((FormatItf) fms::invoke).apply("Testing %s %d %x", "One", new Integer(2), 3));
      assertEquals("Testing One 2 3 four", ff2.apply("Testing %s %d %x %s", "One", new Integer(2), 3, "four"));
  }

  public void testVoid() throws Throwable {
      MethodType pmt = MethodType.methodType(void.class, int.class, Object.class);
      MethodHandle pms = lookup.findVirtual(List.class, "add", pmt);
      List<String> list = new ArrayList<>();

      // --- List.add(int,String) ---

      pms.invoke(list, 0, "Hi");

      AddItf pf2 = pms::invoke;
      pf2.apply(list, 1, "there");
      AddItf pf3 = pms::invokeExact;
      pf3.apply(list, 2, "you");
      assertEquals("Hi", list.get(0));
      assertEquals("there", list.get(1));
      assertEquals("you", list.get(2));
   }
}

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