testa.java

来自「java的23中设计模式的代码实现」· Java 代码 · 共 18 行

/**
 *  A test for SingletonA
 */
public class TestA  {
    public static void main(String[] args) {
        // Can not create a instance !
        //SingletonA instance1 = new SingletonA();  
        SingletonA instance2 = SingletonA.getInstance();
        if(instance2 != null) {
            instance2.setNum();
            System.out.println("i is:" + instance2.getNum());
        }
        SingletonA instance3 = SingletonA.getInstance();
        if(instance3 == null) {
            System.out.println("Can not get instance twice !");   
        }
    }
}