单例<件>模式
1.急切实例化 <饿汉>
public class Singleton {
private static Singleton uniqueInstance = new Singleton();
private Singleton() {}
public static Singleton getInstance() {
return uniqueInstance;
}
}
2.同步getInstance()方法
public class Singleton{
private SingleTone() {}
public static synchronized Singleton getInstance() {
if (uniqueInstance == null) {
uniqueInstance = new Singleton();
}
return uniqueInstance;
}
}
3.双重检查枷锁 <性能比同步getInstance()好, 需要JDK Java5或以上>
public class Singleton {
private volatile static Singleton uniqueInstance;
private Singleton() {}
public static Singleton getInstance() {
if (uniqueInstance == null) {
synchronized (Singleton.class) {
if (uniqueInstance == null) {
uniqueInstance = new Singleton();
}
}
}
}
}
