java的范型约束

 public static <T extends Comparable<? super T>> void sort(List<T> list) {
	Object[] a = list.toArray();
	Arrays.sort(a);
	ListIterator<T> i = list.listIterator();
	for (int j=0; j<a.length; j++) {
	    i.next();
	    i.set((T)a[j]);
	}
    }

　　

From: JDK Collections.sort方法