RuntimeTest

RuntimeTest是一个Java类，它提供了一些方法来获取JVM的运行时信息，例如内存使用情况，线程信息等。以下是一些使用RuntimeTest的例子：

1. 获取JVM可用的最大内存，已用内存，空闲内存[^1]：

Runtime runtime = Runtime.getRuntime();
long maxMemory = runtime.maxMemory();
long totalMemory = runtime.totalMemory();
long freeMemory = runtime.freeMemory();

System.out.println("Max memory: " + maxMemory);
System.out.println("Total memory: " + totalMemory);
System.out.println("Free memory: " + freeMemory);

2. 获取JVM中线程的数量[^2]：

ThreadGroup rootGroup = Thread.currentThread().getThreadGroup().getParent();
while (rootGroup.getParent() != null) {
    rootGroup = rootGroup.getParent();
}
int threadCount = rootGroup.activeCount();

System.out.println("Thread count: " + threadCount);

3. 执行外部程序[^3]：

Process process = Runtime.getRuntime().exec("ls -al");
BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
    System.out.println(line);
}