While it is technically correct to use a Thread where a Runnable is called for, the semantics of the two objects are different, and mixing them is a bad practice that will likely lead to headaches in the future.

The crux of the issue is that Thread is a larger concept than Runnable. A Runnable is an object whose running should be managed. A Thread expects to manage the running of itself or other Runnables.

Noncompliant Code Example

	public static void main(String[] args) {
		Thread r =new Thread() {
			int p;
			@Override
			public void run() {
				while(true)
					System.out.println("a");
			}
		};
		new Thread(r).start();  // Noncompliant

Compliant Solution

	public static void main(String[] args) {
		Runnable r =new Runnable() {
			int p;
			@Override
			public void run() {
				while(true)
					System.out.println("a");
			}
		};
		new Thread(r).start();