饿汉模式
public class Singleton {
private static Singleton instance = new Singleton();
private Singleton (){}
public static Singleton getInstance() {
return instance;
}
}
另类饿汉单例模式(静态代码块)
public class Singleton {
private Singleton instance = null;
static {
instance = new Singleton();
}
private Singleton (){}
public static Singleton getInstance() {
return this.instance;
}
}
懒汉模式 (懒汉,线程安全)
public class Singleton{
private static Singleton instance;
private Singleton(){}
public static synchronized Singleton getInstance(){
if(instance==null){
instance=new Singleton();
}
return instance;
}
}
懒汉模式 (懒汉,线程安全)--双检锁模式
public class Singleton {
private volatile static Singleton singleton;
private Singleton (){}
public static Singleton getSingleton() {
if (singleton == null) {
synchronized (Singleton.class) {
if (singleton == null) {
singleton = new Singleton();
}
}
}
return singleton;
}
}
静态内部类
public class Singleton {
private static class SingletonHolder {
private static final Singleton INSTANCE = new Singleton();
}
private Singleton (){}
public static final Singleton getInstance() {
return SingletonHolder.INSTANCE;
}
}