InheritableThreadLocal & ThreadLocal

InheritableThreadLocalはThreadLocalよりも多くの特性を持ち、継承性があり、親スレッドから初期値を得ることができます.
 
コードの例

public class TestThreadLocal {
	static final String VALUE01 = "VALUE01";
	static final String VALUE02 = "VALUE02";

	public static void main(String[] args) throws InterruptedException {
		ThreadLocal<String> threadLocal = new ThreadLocal<String>();
		threadLocal.set(VALUE01);

		InheritableThreadLocal<String> inheritableThreadLocal = new InheritableThreadLocal<String>();
		inheritableThreadLocal.set(VALUE01);

		Thread thread_1 = new Thread_TestThreadLocal(threadLocal, inheritableThreadLocal);
		thread_1.setName("Thread01");
		thread_1.start();

		thread_1.join();

		System.out.println(Thread.currentThread().getName() + "******************************************");
		System.out.println(Thread.currentThread().getName() + "\tThreadLocal: " + threadLocal.get());
		System.out.println(Thread.currentThread().getName() + "\tInheritableThreadLocal: " + inheritableThreadLocal.get());
	}
}

class Thread_TestThreadLocal extends Thread {
	ThreadLocal<String> threadLocal;
	InheritableThreadLocal<String> inheritableThreadLocal;

	public Thread_TestThreadLocal(ThreadLocal<String> threadLocal, InheritableThreadLocal<String> inheritableThreadLocal) {
		super();
		this.threadLocal = threadLocal;
		this.inheritableThreadLocal = inheritableThreadLocal;
	}

	public void run() {
		System.out.println(Thread.currentThread().getName() + "******************************************");
		System.out.println(Thread.currentThread().getName() + "\tThreadLocal: " + threadLocal.get());
		System.out.println(Thread.currentThread().getName() + "\tInheritableThreadLocal: " + inheritableThreadLocal.get());

		threadLocal.set(TestThreadLocal.VALUE02);
		inheritableThreadLocal.set(TestThreadLocal.VALUE02);

		System.out.println(Thread.currentThread().getName() + "(Reset Value)*****************************");
		System.out.println(Thread.currentThread().getName() + "\tThreadLocal: " + threadLocal.get());
		System.out.println(Thread.currentThread().getName() + "\tInheritableThreadLocal: " + inheritableThreadLocal.get());
	}
}

しゅつりょく
Thread01******************************************
Thread01 ThreadLocal: null
Thread01 InheritableThreadLocal: VALUE01
Thread01(Reset Value)**************************
Thread01 ThreadLocal: VALUE02
Thread01 InheritableThreadLocal: VALUE02
main******************************************
main ThreadLocal: VALUE01
main InheritableThreadLocal: VALUE01