下面的方法尝试从java.lang.management.ManagementFactory中提取PID:

private static String getProcessId(final String fallback) {
    // Note: may fail in some JVM implementations
    // therefore fallback has to be provided

    // something like '<pid>@<hostname>', at least in SUN / Oracle JVMs
    final String jvmName = ManagementFactory.getRuntimeMXBean().getName();
    final int index = jvmName.indexOf('@');

    if (index < 1) {
        // part before '@' empty (index = 0) / '@' not found (index = -1)
        return fallback;
    }

    try {
        return Long.toString(Long.parseLong(jvmName.substring(0, index)));
    } catch (NumberFormatException e) {
        // ignore
    }
    return fallback;
}

例如，只需调用getProcessId("<PID>")。

对于旧的JVM，在linux中…

private static String getPid() throws IOException {
    byte[] bo = new byte[256];
    InputStream is = new FileInputStream("/proc/self/stat");
    is.read(bo);
    for (int i = 0; i < bo.length; i++) {
        if ((bo[i] < '0') || (bo[i] > '9')) {
            return new String(bo, 0, i);
        }
    }
    return "-1";
}

下面的方法尝试从java.lang.management.ManagementFactory中提取PID:

private static String getProcessId(final String fallback) {
    // Note: may fail in some JVM implementations
    // therefore fallback has to be provided

    // something like '<pid>@<hostname>', at least in SUN / Oracle JVMs
    final String jvmName = ManagementFactory.getRuntimeMXBean().getName();
    final int index = jvmName.indexOf('@');

    if (index < 1) {
        // part before '@' empty (index = 0) / '@' not found (index = -1)
        return fallback;
    }

    try {
        return Long.toString(Long.parseLong(jvmName.substring(0, index)));
    } catch (NumberFormatException e) {
        // ignore
    }
    return fallback;
}

例如，只需调用getProcessId("<PID>")。

基于Ashwin Jayaprakash的答案(+1) 关于Apache 2.0许可的SIGAR，下面是我如何使用它来获得当前进程的PID:

import org.hyperic.sigar.Sigar;

Sigar sigar = new Sigar();
long pid = sigar.getPid();
sigar.close();

尽管它不能在所有平台上工作，但它可以在Linux、Windows、OS X和这里列出的各种Unix平台上工作。

您可以尝试在JNR-Posix中的getpid()。

它有一个Windows POSIX包装器，从libc调用getpid()。

试试西格尔。非常广泛的api。Apache 2 license。

private Sigar sigar;

public synchronized Sigar getSigar() {
    if (sigar == null) {
        sigar = new Sigar();
    }
    return sigar;
}

public synchronized void forceRelease() {
    if (sigar != null) {
        sigar.close();
        sigar = null;
    }
}

public long getPid() {
    return getSigar().getPid();
}