test/jdk/com/sun/management/OperatingSystemMXBean/GetSystemCpuLoad.java

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/*
 * @test
 * @bug     7028071
 * @summary Basic unit test of OperatingSystemMXBean.getProcessCpuLoad()
 * @library /test/lib
 * @run main GetSystemCpuLoad
 */

import com.sun.management.OperatingSystemMXBean;
import java.lang.management.*;
import jdk.test.lib.Platform;

public class GetSystemCpuLoad {
    public static void main(String[] argv) throws Exception {
        OperatingSystemMXBean mbean = (com.sun.management.OperatingSystemMXBean)
            ManagementFactory.getOperatingSystemMXBean();

        Exception ex = null;
        double load;

        for (int i = 0; i < 10; i++) {
            load = mbean.getSystemCpuLoad();
            if (load == -1.0 && Platform.isWindows()) {
                // Some Windows 2019 systems can return -1 for the first few reads.
                // Remember a -1 in case it never gets better.
                ex = new RuntimeException("getSystemCpuLoad() returns " + load
                         + " which is not in the [0.0,1.0] interval");

            } else if (load < 0.0 || load > 1.0) {
                throw new RuntimeException("getSystemCpuLoad() returns " + load
                           + " which is not in the [0.0,1.0] interval");
            } else {
                // A good reading: forget any previous -1.
                ex = null;
            }
            try {
                Thread.sleep(200);
            } catch(InterruptedException e) {
                e.printStackTrace();
            }
        }

        if (ex != null) {
            throw ex;
        }
    }
}