Java 多線程下，2種安全、性能靠譜的單例模式

懶漢式-雙重覈驗：

package com.zzf.concurrence.singleinstance;


/**
 * 懶漢式-雙重覈驗
 * @author zzf
 *
 */
public class SingleEHan {
	
	private SingleEHan() {}
	
	private static volatile SingleEHan instance=null;
	
	private static SingleEHan getInstance() {
		
		if(instance==null) {
			synchronized (SingleEHan.class) {
				if(instance==null) //再一次校驗，是因爲多線程情況下，如果 SingleEHan 內容比例多未完全初始完，防止多次new
				instance =new SingleEHan();
			}
		}
		return instance;
	}

}

 

懶漢式-類初始化模式

package com.zzf.concurrence.singleinstance;

/**
 * 懶漢式-類初始化模式
 * 
 * @author zzf
 *
 */
public class SingleInstance {

	private SingleInstance() {
	}

	private static class InstanceHolder {
		public static SingleInstance instance = new SingleInstance();
	}

	public static SingleInstance getInstance() {
		return InstanceHolder.instance;
	}

}

餓漢式：

public class SingleEHan {
    public static SingleEHan singleEHan = new SingleEHan();
    private SingleEHan(){}

}