-首先:

-1將構造方法私有化

-2.定義一個靜態成員方法

-飢餓模式

直接建立一個物件出來

private Student(){}

private static Student student = new Student();

publicstatic Student getInstance(){

return student;

}

-慵懶模式:

只有第一個使用的時候才開始建立一個物件

private static Teacher teacher = null;

private static Object block = new Object();

private Teacher(){}

public Teacher getInstance(){

if(teacher==null)

synchronized(block){

if(teacher==null){

teacher = new Teacher();

}

}

}

return teacher;

}