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/*
目的：分析一下单例设计模式中，懒汉式与饿汉式在多线程中的不同！
开发时我们一般选择饿汉式，因为它简单明了，多线程中不会出现安全问题！
而饿汉式需要我们自己处理程序中存在的安全隐患，但是饿汉式的程序技术含量更高！
*/
/* class SinglePerson implements Runnable{
private static SinglePerson ss = new SinglePerson("hjz", 22);//恶汉式
private int age;
private String name;
private int count;
private SinglePerson(String name, int age){
this.age = age;
this.name = name;
}
private SinglePerson(){
age = 10;
name = " ";
}
public static SinglePerson getInstance(){
return ss;
}
public String getName(){
return name;
}
public int getAge(){
return age;
}
public void setIntroduceCount(){
++count;
}
public int getIntroduceCount(){
return count;
}
public synchronized void run(){
ss.setIntroduceCount();
try{
Thread.sleep(20);
}catch(InterruptedException e){
}
System.out.println("this is " + ss.getName() + " " + ss.getAge() + " 被介绍的次数是：" + ss.getIntroduceCount());
}
} */
class
SinglePerson
implements
Runnable{
private
static
SinglePerson ss =
null
;
//懒汉式
private
int
age;
private
String name;
private
int
count;
private
SinglePerson(String name,
int
age){
this
.age = age;
this
.name = name;
count=
0
;
}
private
SinglePerson(){
age =
10
;
name =
" "
;
}
/*public static SinglePerson getInstance(){
if(ss==null){//单例设计模式中，懒汉式在多线程中的缺憾啊！可能不能保证对象的唯一性
try{
Thread.sleep(10);
}catch(InterruptedException e){}
ss = new SinglePerson("hjz", 22);
}
return ss;
}*/
/* public static synchronized SinglePerson getInstance(){//保证了对象的唯一性，也就是安全性保证了！但是每当调用该函数时
if(ss==null){ //都要判断一下同步锁对象，降低了程序的效率！
try{
Thread.sleep(10);
}catch(InterruptedException e){}
ss = new SinglePerson("hjz", 22);
}
return ss;
} */
public
static
SinglePerson getInstance(){
//这就是懒汉式的安全又效率的代码！
if
(ss==
null
){
//这一句是必须判断的！
synchronized
(SinglePerson.
class
){
//这一句只是其他的线程访问时判断
if
(ss==
null
){
try
{
Thread.sleep(
10
);
}
catch
(InterruptedException e){}
ss =
new
SinglePerson(
"hjz"
,
22
);
}
}
}
return
ss;
}
public
String getName(){
return
name;
}
public
int
getAge(){
return
age;
}
public
void
setIntroduceCount(){
++count;
}
public
int
getIntroduceCount(){
return
count;
}
public
synchronized
void
run(){
ss.setIntroduceCount();
System.out.println(
"this is "
+ ss.getName() +
" "
+ ss.getAge() +
" 被介绍的次数是："
+ ss.getIntroduceCount());
}
}
class
OtherThread
extends
Thread{
public
void
run(){
SinglePerson.getInstance().run();
}
}
public
class
Test{
public
static
void
main(String[] args){
new
OtherThread().start();
new
OtherThread().start();
new
OtherThread().start();
new
Thread(SinglePerson.getInstance()).start();
}
}
|
本文转自 小眼儿 博客园博客，原文链接：http://www.cnblogs.com/hujunzheng/p/3876539.html，如需转载请自行联系原作者
