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/*

 * @test TestSelectDefaultGC

 * @summary Test selection of GC when no GC option is specified

 * @bug 8068582

 * @key gc

 * @library /testlibrary

 * @requires vm.gc=="null"

 * @modules java.base/jdk.internal.misc

 *          java.management

 * @run driver TestSelectDefaultGC

 */

import jdk.test.lib.*;

import java.util.regex.*;

public class TestSelectDefaultGC {

    public static void assertVMOption(OutputAnalyzer output, String option, boolean value) {

        output.shouldMatch(" " + option + " .*=.* " + value + " ");

    }

    public static void testDefaultGC(boolean actAsServer) throws Exception {

        String[] args = new String[] {

          "-XX:" + (actAsServer ? "+" : "-") + "AlwaysActAsServerClassMachine",

          "-XX:" + (actAsServer ? "-" : "+") + "NeverActAsServerClassMachine",

          "-XX:+PrintFlagsFinal",

          "-version"

        };

        // Start VM without specifying GC

        ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(args);

        OutputAnalyzer output = new OutputAnalyzer(pb.start());

        output.shouldHaveExitValue(0);

        final boolean isServer = actAsServer;

        // Verify GC selection

        // Serial is default for non-server class machines

        assertVMOption(output, "UseSerialGC",        !isServer);

        // CMS is never default

        assertVMOption(output, "UseConcMarkSweepGC", false);

        assertVMOption(output, "UseParNewGC",        false);

    }

    public static void main(String[] args) throws Exception {

        // Test server class machine

        testDefaultGC(false);

        // Test non-server class machine

        testDefaultGC(true);

    }

}