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Java example source code file (LambdaStepTest.java)

This example Java source code file (LambdaStepTest.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

breakpointevent, defaulttest, exception, jdi, lambdasteptesttarg, localvariable, runnable, stackframe, stepevent, string, stringreference, testscaffold, threadreference, unexpected

The LambdaStepTest.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.
 *
 * 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 Test stepping through lambdas
 *
 *  @author Staffan Larsen
 *
 *  @run build TestScaffold VMConnection TargetListener TargetAdapter
 *  @run compile -g LambdaStepTest.java
 *  @run main LambdaStepTest
 */
import com.sun.jdi.LocalVariable;
import com.sun.jdi.ObjectReference;
import com.sun.jdi.ReferenceType;
import com.sun.jdi.StackFrame;
import com.sun.jdi.StringReference;
import com.sun.jdi.ThreadReference;
import com.sun.jdi.event.BreakpointEvent;
import com.sun.jdi.event.StepEvent;

 /********** target program **********/

interface DefaultTest {
    default void defaultMethod() {
        String from = "default";
        System.out.println("Hello from " + from);
    }
}
class LambdaStepTestTarg implements DefaultTest {
    private void test() {
        String from = "test";
        System.out.println("Hello from " + from);
    }
    private static void instanceTest() {
        LambdaStepTestTarg l = new LambdaStepTestTarg();
        l.test();
    }
    private static void lambdaTest() {
        Runnable r = () -> {
            String from = "lambda";
            System.out.println("Hello from " + from);
        };
        r.run();
    }
    private static void defaultTest() {
        LambdaStepTestTarg l = new LambdaStepTestTarg();
        l.defaultMethod();
    }
    public static void main(String[] args) {
        instanceTest();
        lambdaTest();
        defaultTest();
        System.out.println("Goodbye from LambdaStepTestTarg!");
    }
}


 /********** test program **********/

public class LambdaStepTest extends TestScaffold {
    LambdaStepTest (String args[]) {
        super(args);
    }

    public static void main(String[] args)
        throws Exception
    {
        new LambdaStepTest (args).startTests();
    }

    /********** test core **********/

    protected void runTests()
        throws Exception
    {
        // ## Normal instance method

        BreakpointEvent bpe = startTo("LambdaStepTestTarg", "instanceTest", "()V");
        ThreadReference thread = bpe.thread();

        // step over allocation
        StepEvent se = stepOverLine(thread);
        System.out.println(se.thread().frame(0));

        // step into test();
        se = stepIntoLine(thread);
        System.out.println(se.thread().frame(0));

        // step over variable initialization
        se = stepOverLine(thread);
        System.out.println(se.thread().frame(0));

        // get value of variable "from"
        StackFrame frame = se.thread().frame(0);
        LocalVariable lv = frame.visibleVariableByName("from");
        System.out.println(lv);
        StringReference sr = (StringReference) frame.getValue(lv);
        if (!sr.value().equals("test")) {
            throw new Exception("Unexpected variable value in instanceTest: "+sr.value());
        }


        // ## Lambda method

        bpe = resumeTo("LambdaStepTestTarg", "lambdaTest", "()V");
        thread = bpe.thread();

        // step over allocation
        se = stepOverLine(thread);
        System.out.println(se.thread().frame(0));

        // step into run() of the lambda
        se = stepIntoLine(thread);
        System.out.println(se.thread().frame(0));

        // step over variable initialization
        se = stepOverLine(thread);
        System.out.println(se.thread().frame(0));

        // get value of variable "from"
        frame = se.thread().frame(0);
        lv = frame.visibleVariableByName("from");
        System.out.println(lv);
        sr = (StringReference) frame.getValue(lv);
        if (!sr.value().equals("lambda")) {
            throw new Exception("Unexpected variable value in lambdaTest: "+sr.value());
        }


        // ## Default method

        bpe = resumeTo("LambdaStepTestTarg", "defaultTest", "()V");
        thread = bpe.thread();

        // step over allocation
        se = stepOverLine(thread);
        System.out.println(se.thread().frame(0));

        // step into defaultMethod()
        se = stepIntoLine(thread);
        System.out.println(se.thread().frame(0));

        // step over variable initialization
        se = stepOverLine(thread);
        System.out.println(se.thread().frame(0));

        // get value of variable "from"
        frame = se.thread().frame(0);
        lv = frame.visibleVariableByName("from");
        System.out.println(lv);
        sr = (StringReference) frame.getValue(lv);
        if (!sr.value().equals("default")) {
            throw new Exception("Unexpected variable value in lambdaTest: "+sr.value());
        }


        /*
         * resume the target listening for events
         */
        listenUntilVMDisconnect();

    }
}

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