jdk-24/test/langtools/tools/javac/switchnull/SwitchNull.java

/*
 * Copyright (c) 2021, 2022, 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
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 * questions.
 */

/*
 * @test
 * @bug 8262891
 * @summary Verify "case null" behavior.
 */

public class SwitchNull {
    public static void main(String... args) {
        SwitchNull instance = new SwitchNull();

        instance.run();
    }

    private void run() {
        assertEquals(0, switchIntegerBox(Integer.MIN_VALUE));
        assertEquals(1, switchIntegerBox(-2));
        assertEquals(2, switchIntegerBox(-1));
        assertEquals(3, switchIntegerBox(0));
        assertEquals(4, switchIntegerBox(1));
        assertEquals(5, switchIntegerBox(2));
        assertEquals(6, switchIntegerBox(Integer.MAX_VALUE));
        assertEquals(-1, switchIntegerBox(null));
        assertEquals(-2, switchIntegerBox(3));
        assertEquals(0, switchString(""));
        assertEquals(1, switchString("a"));
        assertEquals(2, switchString("A"));
        assertEquals(-1, switchString(null));
        assertEquals(-2, switchString("c"));
        assertEquals(0, switchEnum(E.A));
        assertEquals(1, switchEnum(E.B));
        assertEquals(2, switchEnum(E.C));
        assertEquals(-1, switchEnum(null));
        assertEquals(0, switchEnumWithDefault(E.A));
        assertEquals(1, switchEnumWithDefault(E.B));
        assertEquals(1, switchEnumWithDefault(E.C));
        assertEquals(-1, switchEnumWithDefault(null));
        testSwitchIntegerBoxExhaustive();
    }

    private int switchIntegerBox(Integer i) {
        switch (i) {
            case Integer.MIN_VALUE: return 0;
            case -2: return 1;
            case -1: return 2;
            case 0: return 3;
            case 1: return 4;
            case 2: return 5;
            case Integer.MAX_VALUE: return 6;
            case null: return -1;
            default: return -2;
        }
    }

    private int switchString(String s) {
        switch (s) {
            case "": return 0;
            case "a": return 1;
            case "A": return 2;
            case null: return -1;
            default: return -2;
        }
    }

    private int switchEnum(E e) {
        switch (e) {
            case A: return 0;
            case B: return 1;
            case C: return 2;
            case null: return -1;
        }
    }

    private int switchEnumWithDefault(E e) {
        switch (e) {
            case A: return 0;
            case null: return -1;
            default: return 1;
        }
    }

    private void testSwitchIntegerBoxExhaustive() {
        int i = Integer.MIN_VALUE;

        do {
            int result = switchIntegerBoxExhaustive(i);
            int expected = i == 0 ? 0 : 1;
            assertEquals(expected, result);
        } while (i++ < Integer.MAX_VALUE);

        int result = switchIntegerBoxExhaustive(null);
        assertEquals(-1, result);
    }

    private int switchIntegerBoxExhaustive(Integer i) {
        return switch (i) {
            case null -> -1;
            case 0 -> 0;
            default -> 1;
        };
    }

    enum E {
        A,
        B,
        C;
    }

    private void assertEquals(int expected, int actual) {
        if (expected != actual) {
            throw new AssertionError("Expected: " + expected + ", actual: " + actual);
        }
    }
}