本帖最后由 新手ing 于 2015-7-19 15:35 编辑
1、写一个程序，两个线程Input和Output。Input交替写数据，output负责读数据。
public class Demo11 {
/**
* 多线程对共享数据的操作
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Resource r = new Resource();
Thread in = new Thread(new Input(r));
Thread out = new Thread(new Output(r));
in.start();
out.start();
}
}
class Input implements Runnable{
private Resource r;
Input(Resource r){
this.r = r ;
}
boolean flag = true;
public void run(){
while(true){
if(flag){
r.name = "zhangsan";
r.sex = "男";
flag = false;
}else{
r.name = "lili";
r.sex = "女";
flag = true;
}
}
}
}
class Output implements Runnable{
private Resource r;
Output(Resource r){
this.r = r;
}
public void run(){
while(true){
System.out.println(r.name+"......"+r.sex);
}
}
}
class Resource{
String name ;
String sex ;
}
从输出结果可以看到：lili输出了男，zhangsan输出了女。为什么会出现这种状况？对共享数据访问时，顺序出现了错误，还没等Input线程处理完，Output开始输出。看一下改进版。
public class Demo11 {
/**
* 多线程对共享数据的操作
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Resource r = new Resource();
Thread in = new Thread(new Input(r));
Thread out = new Thread(new Output(r));
in.start();
out.start();
}
}
class Input implements Runnable {
private Resource r;
Input(Resource r) {
this.r = r;
}
boolean flag = true;
public void run() {
while (true) {
synchronized (r) {
if (flag) {
r.name = "zhangsan";
r.sex = "男";
flag = false;
} else {
r.name = "lili";
r.sex = "女";
flag = true;
}
}
}
}
}
class Output implements Runnable {
private Resource r;
Output(Resource r) {
this.r = r;
}
public void run() {
while (true) {
synchronized (r) {
System.out.println(r.name + "......" + r.sex);
}
}
}
}
class Resource{
String name ;
String sex ；
}
现在更改一下需求：要求zhangsan和lili交替输出。
public class Demo11 {
/**
* 多线程对共享数据的操作
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Resource r = new Resource();
Thread in = new Thread(new Input(r));
Thread out = new Thread(new Output(r));
in.start();
out.start();
}
}
class Input implements Runnable {
private Resource r;
Input(Resource r) {
this.r = r;
}
boolean flag = true;
public void run() {
int x = 0;
while (true) {
synchronized (r) {
if(r.flag){
try {
r.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (x==0) {
r.name = "zhangsan";
r.sex = "男";
} else {
r.name = "lili";
r.sex = "女";
}
x=(x+1)%2;
r.flag = true;
r.notify();
}
}
}
}
class Output implements Runnable {
private Resource r;
Output(Resource r) {
this.r = r;
}
public void run() {
while (true) {
synchronized (r) {
if(!r.flag){
try {
r.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println(r.name + "......" + r.sex);
r.flag = false;
r.notify();
}
}
}
}
class Resource{
String name ;
String sex ;
boolean flag = false;
}
代码优化一下
public class Demo11 {
/**
* 多线程对共享数据的操作
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Resource r = new Resource();
Thread in = new Thread(new Input(r));
Thread out = new Thread(new Output(r));
in.start();
out.start();
}
}
class Input implements Runnable {
private Resource r;
Input(Resource r) {
this.r = r;
}
boolean flag = true;
public void run() {
int x = 0;
while (true) {
if(x==0){
r.set("zhangsan", "男");
}else{
r.set("lili", "女");
}
x = (x+1)%2;
}
}
}
class Resource{
private String name ;
private String sex ;
boolean flag = false;
public synchronized void set(String name ,String sex){
if(flag){
try {
this.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
this.name = name ;
this.sex = sex;
flag = true;
this.notify();
}
public synchronized void info(){
if(!flag){
try {
this.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println(name + "......" + sex);
flag = false;
this.notify();
}
}
class Output implements Runnable {
private Resource r;
Output(Resource r) {
this.r = r;
}
public void run() {
while (true) {
r.info();
}
}
}
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