巧用ENUM 实现 Thread－safe Singleton
其实Enum 类本身就是一个Class 唯一不同的就是这个class的构造函数是private类型的。其他enum具有所有class具有的特性。
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public class EnumTest {
??? public static void main(String args[]){
??? ??? EnumTest eTest = new EnumTest();
??? ??? List<Thread> threads = new ArrayList<Thread>();
??? ??? for(int i=0;i<10;i++){
??? ??? ??? threads.add(new Thread(eTest.new TT()));
??? ??? }
??? ??? for (Thread thread : threads) {
??? ??? ??? thread.start();
??? ??? }
??? }
???
??? @SuppressWarnings({"rawtypes", "unchecked"})
??? private enum ComparableComparator implements Comparator {
??? ??? INSTANCE;
??? ??? /**
??? ???? * Comparable based compare implementation.
??? ???? *
??? ???? * @param obj1 left hand side of comparison
??? ???? * @param obj2 right hand side of comparison
??? ???? * @return negative, 0, positive comparison value
??? ???? */
??? ??? public int compare(Object obj1, Object obj2) {
??? ??????? return ((Comparable) obj1).compareTo(obj2);
??? ??? }
??? }
???
??? private class TT implements Runnable{
??? ??? int count=10;
??? ??? @Override
??? ??? public void run() {
??? ??? ??? for(int i=0;i<count;i++){
??? ??? ??? ??? System.out.println(ComparableComparator.INSTANCE.hashCode());
??? ??? ??? }
??? ??? }
??? ???
??? }
}
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这样通过调用ComparableComparator 枚举实例INSTANCE 就达到了threa－safe 的singleton
