objbalances.java

介绍有关java的资料 课件 相当一本书籍 里面都是很基础的知识

package objbalances;
// 多个出纳员对多个账户同时操作而让账户保持平衡。
import java.awt.*;
import java.util.*;
class ObjBalances extends Frame {
  Label names[];
  TextField sbalances[];
  Button start,stop,exit;
  int sum;
  Customer customers[];
  Teller teller1, teller2, teller3;
  //-----------------------------------
  public ObjBalances() {
    super("银行平衡表");
    setLayout(new BorderLayout());
    setBackground(Color.lightGray);
    Panel p1 = new Panel();
    Panel p2 = new Panel();
    add("South", p2);
    add("Center", p1);
    p1.setLayout(new GridLayout(6, 2));
    sbalances = new TextField[6];
    sum = 0;
    names = new Label[6];
    names[0] = new Label("张三");
    names[1]= new Label("李四");
    names[2] = new Label("王五");
    names[3] = new Label("赵六");
    names[4] = new Label("侯七");
    names[5] = new Label("总计");
    customers = new Customer[5];
    for (int i =0; i< 5; i++) {
      customers[i]= new Customer(1000);
      int b = customers[i].getBalance();
      sum += b;
      sbalances[i] = new TextField(new Integer(b).toString());
      Panel p = new Panel();
      p1.add(p);
      p1.add(names[i]);
      p.add(sbalances[i]);
      p1.add(p);
    }
    sbalances[5] = new TextField(new Float(sum).toString());
    Panel p = new Panel();
    p1.add(names[5]);
    p1.add(p);
    p.add(sbalances[5]);
    start = new Button("开始");
    stop = new Button("停止");
    exit = new Button("退出");
    p2.add(start);
    p2.add(stop);
    p2.add(exit);
    reshape(100,100,300,250);
    show();
    }
    //-----------------------------------
    public void paint(Graphics g) {
    float sum =0;
    for (int i=0; i< 5; i++) {
      int b = customers[i].getBalance();
      sbalances[i].setText(new Integer(b).toString());
      sum += b;
    }
    sbalances[5].setText( new Float(sum).toString());
  }
  //-----------------------------------
  public void clickedStart() {
    teller1 = new Teller(customers, 5, 1);
    teller2 = new Teller(customers, 5, 5);
    teller3 = new Teller(customers, 5, 7);
    teller1.start();
    teller2.start();
    teller3.start();
    start.disable();
  }
  //-----------------------------------
  public void clickedStop() {
    teller1.stoppit();
    teller2.stoppit();
    teller3.stoppit();
    start.enable();
    repaint();
  }
  //-----------------------------------
  public boolean action(Event evt, Object arg) {
    if (evt.target == start){
      clickedStart();
      return true;
    }
    else
      if (evt.target == stop) {
        clickedStop();
        return true;
      }
      else
        if(evt.target == exit){
          System.exit(0);
          return true;
        }
        else
          return super.action(evt, arg);
  }
  //-----------------------------------
  public static void main(String argv[]) {
    new ObjBalances();
  }
}
//==========================================
class Customer {
  int balance;
  //-----------------------------------
  public Customer(int money) {
    balance = money;
  }
  //-----------------------------------
  // synchronized public void changeLedger(int value)
  public void changeLedger(int value) {
    balance += value;
  }
  //-----------------------------------
  public int getBalance() {
    return balance;
  }
}
//==========================================
class Teller extends Thread {
  int count;
  int amount;
  Customer cust[];
  boolean stop_flag;
  //-----------------------------------
  public Teller(Customer cst[], int cnt, int amt) {
    count = cnt;
    amount = amt;
    cust = cst;
    stop_flag = false;
  }
  //-----------------------------------
  public void stoppit() {
    stop_flag = true;
  }
  //-----------------------------------
  public void run() {
    Customer custf, custto;
    while (true) {
      int from = (int)Math.round(Math.random() *(count-1));
      int to = (int)Math.round(Math.random() *(count-1));
      if (from != to) {
        custf = (Customer)cust[from];
        custto = (Customer)cust[to];
        synchronized(custf) {
          custf.changeLedger(-amount);
        }
        synchronized(custto) {
          custto.changeLedger(amount);
        }
      } //end if
      if (stop_flag) stop();
    } //end while
  }
}