public class A{
private static A a = null;
private A(){}
public static A getInstance(){
if (a == null){
synchronized(A.class){
if(a == null){
a = new A();
}
}
}
return a;
}
}
public class A{
private A(){}
public static A getInstance(){
return AHolder.instance;
}
private static class AHolder{
private static final A instance = new A();
}
}
枚舉單例
public enum A{
INSTANCE;
public void doSomething(){
System.out.println("");
}
}
