单例模式

package mode.single;public class Single {private static Single single;private Single() {}public static Single getInstance() {if (null == single) {System.out.println("第一次创建");single = new Single();}return single;}}

测试

package mode.single;public class Test {public static void main(String[] args) {Single s1 = Single.getInstance();Single s2 = Single.getInstance();Single s3 = Single.getInstance();}}