单例模式

饱汉模式：

packagecom.jerry.design.singleton;

publicclassFullSingle {

privatestaticFullSingleinstance=null;

privateFullSingle(){

}

publicsynchronizedstaticFullSingle getIntance(){

if(instance==null){

instance=newFullSingle();

}

returninstance;

}

}

饿汉模式：

packagecom.jerry.design.singleton;

publicclassHungrySingle {

privatestaticHungrySingleinstance=newHungrySingle();

privateHungrySingle(){

}

publicstaticHungrySingle getIntance(){

returninstance;

}

}

测试代码：

packagecom.jerry.design.singleton;

publicclassTest {

publicstaticvoidmain(String[] args) {

for(inti=0;i<=10;i++){

System.out.println(FullSingle.getIntance());

System.out.println(HungrySingle.getIntance());

}

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

// com.jerry.design.singleton.FullSingle@3487a5cc

// com.jerry.design.singleton.HungrySingle@eb42cbf

}

}

总结: 保持单jvm下的唯一实例。