java单例的几种实现方法：
方式1：
public class Something {
private Something() {}
private static class LazyHolder {
private static final Something INSTANCE = new Something();
}
public static Something getInstance() {
return LazyHolder.INSTANCE;
}}
方式2：
public class Singleton {
private static final Singleton INSTANCE = new Singleton();
private Singleton() {}
public static Singleton getInstance() {
return INSTANCE;
}}
方式3：
public class Singleton {
private static final Singleton instance;
static {
try {
instance = new Singleton();
} catch (Exception e) {
throw new RuntimeException("Darn, an error occurred!", e);
}
}
public static Singleton getInstance() {
return instance;
}
private Singleton() {
// ...
}}
方式4：
public enum Singleton {
INSTANCE;
public void execute (String arg) {
// Perform operation here
}}
方式5：
public class SingletonDemo {
private static volatile SingletonDemo instance;
private SingletonDemo() { }
public static SingletonDemo getInstance() {
if (instance == null ) {
synchronized (SingletonDemo.class) {
if (instance == null) {
instance = new SingletonDemo();
}
}
}
return instance;
}}
方式6：
使用apache commons lang: LazyInitializer
public class ComplexObjectInitializer extends LazyInitializer {
@Override
protected ComplexObject initialize() {
return new ComplexObject();
}}
// Create an instance of the lazy initializer
ComplexObjectInitializer initializer = new ComplexObjectInitializer();
...
// When the object is actually needed:
ComplexObject cobj = initializer.get();
方式7：
使用guava：
private static final Supplier tokenSup = Suppliers.memoize(new Supplier() {
@Override
public String get() {
//do some init
String result = xxx;
return result;
}
});
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本文转自被遗忘的博客园博客，原文链接：http://www.cnblogs.com/rollenholt/p/4774063.html，如需转载请自行联系原作者
