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电脑
Eclipse
·1 第一步：打开编译器然后再点开一个java文件。
2第二步：在文件里右击鼠标，然后再选择Preferences。
3第三步：而后再Preferences里选择java
4第四步：再选择Editor,再选择Content Assist
5 第五步：再在所圈出的地方设置时间（200）和字母（.ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz），而后点击ok即可。
楼主，依题意，完整的程序如下：
import java.awt.FlowLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Exam2 extends Thread implements ActionListener
{
//声明界面元素
private JFrame timeFrame;
private JButton startButton;
private JButton stopButton;
private JButton resetButton;
private JLabel timeLabel;
//定义变量存储时、分、秒
int hour = 0;
int minute = 0;
int second = 0;
//声明线程对象
Thread myThread;
public Exam2()
{
timeFrame = new JFrame("计时器");
startButton = new JButton("开始");
stopButton = new JButton("停止");
resetButton = new JButton("重置");
timeLabel = new JLabel("00:00:00");
timeFrame.setLayout(new FlowLayout());
timeFrame.setBounds((Toolkit.getDefaultToolkit().getScreenSize().width - 300)/2,
(Toolkit.getDefaultToolkit().getScreenSize().height - 200)/2, 300, 200);
timeFrame.add(timeLabel);
timeFrame.add(startButton);
timeFrame.add(stopButton);
timeFrame.add(resetButton);
timeFrame.setVisible(true);
timeFrame.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
startButton.addActionListener(this);
stopButton.addActionListener(this);
resetButton.addActionListener(this);
myThread = this;
}
public void actionPerformed(ActionEvent e)
{
if(e.getSource() == this.startButton)
{
System.out.println("计时开始...");
if(this.start)
{
this.myThread.start();
}
else
{
this.start = true;
}
}
if(e.getSource() == this.stopButton)
{
System.out.println("计时停止...");
this.start = false;
}
if(e.getSource() == this.resetButton)
{
hour = 0;
minute = 0;
second = 0;
}
}
volatile boolean start = true;
@Override
public void run()
{
while(true)
{
if(this.start)
{
second++;
try
{
Thread.sleep(1000);
} catch (InterruptedException e)
{
e.printStackTrace();
}
if(second = 60)
{
second = 0;
minute++;
}
if(minute = 60)
{
minute = 0;
hour++;
}
showTime();
}
}
}
private void showTime()
{
String strTime = "";
if(hour 10)
{
strTime += "0"+hour + ":";
}
else
{
strTime += hour + ":";
}
if(minute 10)
{
strTime += "0"+minute + ":";
}
else
{
strTime += minute + ":";
}
if(second 10)
{
strTime += "0"+second;
}
else
{
strTime += second;
}
this.timeLabel.setText(strTime);
}
public static void main(String[] args)
{
new Exam2();
}
}
有问题欢迎提问，满意请采纳，谢谢！
package xinguan;
abstract class Operation{ //抽象类
public static double numberA= 0;
public static double numberB = 0;
abstract double getResult(); //抽象方法
}
class OperationADD extends Operation{
@Override
double getResult() {
return numberA+numberB;
}
}
class OperationSUB extends Operation{
@Override
double getResult() {
return numberA-numberB;
}
}
class OperationMUL extends Operation{
@Override
double getResult() {
return numberA*numberB;
}
}
class OperationDIV extends Operation{
@Override
double getResult() {
return numberA/numberB;
}
}
class OperationFactory{
public static Operation createOperate(char operate){
Operation oper = null;
switch (operate){
case'+':
oper= new OperationADD();
break;
case'-':
oper= new OperationSUB();
break;
case'*':
oper= new OperationMUL();
break;
case'/':
oper= new OperationDIV();
break;
}
return oper;
}
}
public class CalculateDemo {
/**
* @param args
*/
public static void main(String[] args) {
Operation operADD = OperationFactory.createOperate('+');
Operation operSUB = OperationFactory.createOperate('-');
Operation operMUL = OperationFactory.createOperate('*');
Operation operDIV = OperationFactory.createOperate('/');
operADD.numberA = 15.0;
operADD.numberB = 3;
System.out.println(operADD.getResult());
System.out.println(operSUB.getResult());
System.out.println(operMUL.getResult());
System.out.println(operDIV.getResult());
}
}
因为抽象类是静态方法 所以 给operADD 那个对象赋值一次就能获得所有结果。要是去掉static 那么就需要每个对象 赋值。现在基本满足你的要求了。
public class ___ArrayUtil___{
public static void _printReversely(String a[])___{
for(int i=___ a.length___ ; i0; i++){//这里不是i++吧,应该是i--
System.out.println(__a[i-1]____);
}
}
}
写完ArrayUtil类后，若要在同一个包中的Decoder类中使用ArrayUtil类中的数组元素倒序打印函数，打印数组{1,2,3,4,5}，则正确的调用方式为（）:
public class Decoder{
public static void main(String args[]){
int a[]={1,2,3,,4,5}
____ArrayUtil.printReversely(a)__________;
}
}
