关于Java:singleton与静态方法和字段？

Singleton class vs static methods and fields?

本问题已经有最佳答案，请猛点这里访问。

为什么在Android／Java中使用单级类，当使用一个具有静态字段和方法的类来提供相同的功能时？

例如

1
2
3
4
5
6
7
8
9
10
11

public class StaticClass {
private static int foo = 0;

public static void setFoo(int f) {
foo = f;
}

public static int getFoo() {
return foo;
}
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

public class SingletonClass implements Serializable {

private static volatile SingletonClass sSoleInstance;
private int foo;

//private constructor.
private SingletonClass(){

//Prevent form the reflection api.
if (sSoleInstance != null){
throw new RuntimeException("Use getInstance() method to get the single instance of this class.");
}

foo = 0;
}

public static SingletonClass getInstance() {
if (sSoleInstance == null) { //if there is no instance available... create new one
synchronized (SingletonClass.class) {
if (sSoleInstance == null) sSoleInstance = new SingletonClass();
}
}

return sSoleInstance;
}

//Make singleton from serialize and deserialize operation.
protected SingletonClass readResolve() {
return getInstance();
}

public void setFoo(int foo) {
this.foo = foo;
}

public int getFoo() {
return foo;
}
}