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Java example source code file (SamConversion.java)

This example Java source code file (SamConversion.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

assertionerror, bar, exception, foo, integer, samconversion, string

The SamConversion.java Java example source code

/*
 * Copyright (c) 2011, 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
 * @bug 8003280
 * @summary Add lambda tests
 *   Test SAM conversion of lambda expressions in context of assignment, method call, return statement and cast.
 * @compile SamConversion.java
 * @run main SamConversion
 */

public class SamConversion {

    static interface Foo {
        Integer m(int i);
    }

    static interface Bar {
        int m(Integer i) throws Exception;
    }

    private static String assertionStr = "";

    private static void assertTrue(boolean b) {
        if(!b)
            throw new AssertionError();
    }

    private static void test1(Foo foo) {
        assertTrue(foo.m(1) == 2);
    }

    private static void test2(Bar bar) {
        try {
            assertTrue(bar.m(1) == 2);
        } catch (Exception e){
            assertTrue(false);
        }
    }

    private static Bar test3(int i) {
        switch (i) {
        case 0:
            return n -> n + 1;
        case 1:
            return (Integer n) -> 2 * n;
        case 2:
            return (Integer n) -> {return new Integer(n-1);};
        case 3:
            return n -> {throw new Exception();};
        default:
            return null;
        }
    }

    public static void main(String[] args) {

        //assign:
        Foo foo = (int n) -> n + 1; //explicit type and boxing
        assertTrue(foo.m(1) == 2);

        foo = n -> n + 1; //type inferrred and boxing
        assertTrue(foo.m(1) == 2);

        Bar bar = (Integer n) -> n + 1; //explicit type and unboxing
        try {
            assertTrue(bar.m(1) == 2);
        } catch (Exception e) {
            assertTrue(false);
        }

        bar = (Integer n) -> new Integer(n+1); //explicit type and unboxing twice
        try {
            assertTrue(bar.m(1) == 2);
        } catch (Exception e) {
            assertTrue(false);
        }

        bar = n -> n.intValue() + 1; //type inferred
        try {
            assertTrue(bar.m(1) == 2);
        } catch (Exception e) {
            assertTrue(false);
        }

        bar = n -> n + 1; // type inferred and unboxing
        try {
            assertTrue(bar.m(1) == 2);
        } catch (Exception e) {
            assertTrue(false);
        }

        //cast:
        assertTrue(((Foo)n -> {return n+1;}).m(1) == 2); //statement (instead of expression) in lambda body
        try {
            assertTrue(((Bar)n -> {return n+1;}).m(1) == 2); //statement in lambda body
        } catch (Exception e) {
            assertTrue(false);
        }

        //method parameter:
        test1((int n) -> new Integer(n+1)); //explicit type
        test2((Integer n) -> n.intValue() + 1); //explicit type

        //return statement:
        bar = test3(0);
        try {
            assertTrue(bar.m(1) == 2);
        } catch (Exception e) {
            assertTrue(false);
        }
        bar = test3(1);
        try {
            assertTrue(bar.m(3) == 6);
        } catch (Exception e) {
            assertTrue(false);
        }
        bar = test3(2);
        try {
            assertTrue(bar.m(10) == 9);
        } catch (Exception e) {
            assertTrue(false);
        }
        bar = test3(3);
        try {
            bar.m(10);
            assertTrue(false);
        } catch (Exception e) {}
    }
}

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