方案一
1
2
3
4
5
6
7
8
9
10
11
12
| public class Singleton {
private static Singleton uniqueInstance;
private Singleton() {}
public static Singleton getInstance() {
if (uniqueInstance == null) {
uniqueInstance = new Singleton();
}
return uniqueInstance;
}
}
|
缺点：无法应对多线程的场景，即使将getInstance()加上synchronized关键字也会带来性能方面的问题。
方案二：饿汉模式
1
2
3
4
5
6
7
8
9
| public class Singleton {
private static Singleton uniqueInstance = new Singleton();
private Singleton() {}
public static Singleton getInstance() {
return uniqueInstance;
}
}
|
方案三：双重检查加锁+饿汉模式
1
2
3
4
5
6
7
8
9
10
11
12
13
14
| 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();
}
}
}
return uniqueInstance;
}
}
|