Java 設(shè)計(jì)模式 單例模式 Singleton
1.懶漢（線程安全）
//懶漢
public class Singleton {
private static Singleton singleton;
private Singleton() {
}
public static synchronized Singleton getSingleton() {
if (singleton == null) {
singleton = new Singleton();
}
return singleton;
}
}
2.餓漢
//餓漢
public class Singleton {
private static final Singleton singleton = new Singleton();
private Singleton () {
}
public static Singleton getSingleton() {
return singleton;
}
}
3.靜態(tài)內(nèi)部類
//靜態(tài)內(nèi)部類
public class Singleton {
private static class SingletonHolder {
private static final Singleton singleton = new Singleton();
}
private Singleton() {
}
public static Singleton getSingleton() {
return SingletonHolder.singleton;
}
}
4.枚舉
//枚舉
public enum Singleton {
INSTANCE;
public void whateverMethod() {
}
}
5.double-lock
//double-lock
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;
}
}
