java單例的幾種實現方法

時間 2019-11-05

標籤 java 幾種實現方法欄目 Java 简体版

原文原文鏈接

java單例的幾種實現方法：

方式1：html

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：java

public class Singleton {
    private static final Singleton INSTANCE = new Singleton();

    private Singleton() {}

    public static Singleton getInstance() {
        return INSTANCE;
    }
}

方式3：apache

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：api

public enum Singleton {
    INSTANCE;
    public void execute (String arg) {
        // Perform operation here 
    }
}

方式5：ide

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：code

使用apache commons lang: LazyInitializerorm

public class ComplexObjectInitializer extends LazyInitializer<ComplexObject> {
     @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：htm

使用guava：token

private static final Supplier<String> tokenSup = Suppliers.memoize(new Supplier<String>() {
        @Override
        public String get() {
            //do some init
            String result = xxx;
            return result;
        }
    });