java之 ------ 多線程（互動線程）

標籤：java   多線程   互動線程   

1、運行結果不惟一，取決於線程調度
2、線程執行被打斷時出現錯誤

3、線程互斥和臨界區管理

1）作業系統對共用一個變數的若干線程進入各自臨界區有以下3個調度原則：
2）一次至多一個線程能夠在它的臨界區內。
3）不能讓一個線程無限地留在它的臨界區內。
4）不能強迫一個線程無限地等待進入它的臨界區。特別地，進入臨界區的任一線程不能妨礙正等待進入的其他線程的進展。

4、同步語句   synchronized (對象)

       同步方法  synchronized  方法聲明   方法聲明synchronized(this){  方法體  }

5、銀行賬戶的存款取款線程

Account.c

package p25;public class Account {private String name;//儲戶姓名private double balance;//賬戶餘額public Account(String name) {this.name = name;this.balance = 0;}//查詢餘額public double balance() {return this.balance;}public String getName() {return this.name;}//存款操作public void put(double value) {if (value > 0) {this.balance += value;}}//取款操作public double get(double value) {if (value > 0) {if (value < this.balance) {//夠取this.balance -= value;} else {value = this.balance;this.balance = 0;}return value;}return 0;}}class Save extends Thread {private Account account;private double value;public Save(Account account, double value) {this.account = account;this.value = value;}public void run() {synchronized (account) {//聲明臨界區，鎖定當前account對象double howmuch = this.account.balance();//查看賬戶餘額try {sleep(1);} catch (InterruptedException e) {e.printStackTrace();}this.account.put(this.value);double howmuch2 = this.account.balance();//查看賬戶餘額System.out.println(this.account.getName() + "賬戶: 現有" + howmuch+ ",存入" + this.value + ",餘額為" + howmuch2);}}}class Fetch extends Thread {private Account account;private double value;public Fetch(Account account, double value) {this.account = account;this.value = value;}public void run() {synchronized (account) {double howmuch = this.account.balance();try {sleep(1);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}double v = this.account.get(this.value);double howmuch2 = this.account.balance();System.out.println(this.account.getName() + "賬戶: 現有" + howmuch+ ",取出" + v + ",餘額為" + howmuch2);}}}class Func extends Thread {private Account account;private double value;public Func(Account account, double value) {this.account = account;this.value = value;}public void run() {fun();}synchronized void fun(){double howmuch = this.account.balance();try {sleep(1);} catch (InterruptedException e) {e.printStackTrace();}this.account.put(this.value);double v = this.account.get(this.value);double howmuch2 = this.account.balance();System.out.println(this.account.getName() + "賬戶: 現有" + howmuch + ",取出"+ v + ",餘額為" + howmuch2);}}

Bank.c

package p25;public class Bank {public static void main(String[] args) {Account wang = new Account("wang");(new Save(wang,100)).start();(new Save(wang,200)).start();(new Fetch(wang,100)).start();Account li=new Account("li");(new Save(li,300)).start();Account xu=new Account("xu");(new Func(xu,100000)).start();}}

註：必須要聲明臨界區，鎖定account對象，不然會出錯
正確結果：

                                          

錯誤結果：

                     

著作權聲明：本文為博主原創文章，未經博主允許不得轉載。

java之 ------ 多線程（互動線程）