简单饿汉式
public class Singleton {
private static Singleton mInstance = new Singleton();
private Singleton(){
}
public static Singleton getInstance(){
return mInstance;
}
public static void main(String arg []){
Singleton mInstance = Singleton.getInstance();
Singleton mInstance2 = Singleton.getInstance();
System.out.println(mInstance);
System.out.println(mInstance2);
}
}
public class Singleton {
private static Singleton mInstance = null;
private Singleton(){
}
public static synchronized Singleton getInstance(){
if(mInstance == null){
mInstance = new Singleton();
}
return mInstance;
}
public static void main(String arg []){
Singleton mInstance = Singleton.getInstance();
Singleton mInstance2 = Singleton.getInstance();
System.out.println(mInstance);
System.out.println(mInstance2);
}
}
public class Singleton {
private static Singleton mInstance = null;
private Singleton(){
}
public static Singleton getInstance(){
if(mInstance == null){
synchronized(Singleton.class){
if(mInstance == null){
mInstance = new Singleton();
}
}
}
return mInstance;
}
public static void main(String arg []){
Singleton mInstance = Singleton.getInstance();
Singleton mInstance2 = Singleton.getInstance();
System.out.println(mInstance);
System.out.println(mInstance2);
}
}
public emun Singleton{
INSTANCE;
private Singleton(){
}
}