问答题
本题的功能是计算1~10之间除了5以外的各个自然数的和。
public class java1
public static void main(String[]args)
int i=1;
int sum=0;
while(i<=10)
if(i==5)
______;
______;
______;
i++;
System.out.println("sum="+sum);
【参考答案】
第1处:i=i+1或i++或i+=1
第2处:continue
第3处:sum+=i或sum=sum+i
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本题的功能是求两个交叉图形的并、减、交和异或。窗口中有4个单选按钮和一个图形面板,面板中有两个交叉的图形,选中其中一个单选按钮,图形面板中以黑色填充的方式显示运算结果。 import java.awt.*; import java.awt.event.*; import java.awt.geom.*; import java.util.*; import javax.swing.*; public class java3 public static void main(String[]args) JFrame frame=new AreaTestFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.show(); class AreaTestFrame extends JFrame public AreaTestFrame() setTitle( java3 ); setSize(WIDTH,HEIGHT); areal =new Area(new Ellipse2D.Double(100,100,150,100)); area2 =new Area(new Rectangle2D.Double(150,150,150,100)); Container confentPane=getContentpane(); panel=new JPanel() public void paintComponent(Graphics g) super.paintComponent(g); Graphics2D g2=(Graphics2D)g; g2.draw(area1); g2.draw(area2); if(area!=null)g2.fill(area); ; contentPane.add(panel,BorderLayout.CENTER); JPanel buttonPanel=new JPanel(); ButtonGroup group=new ButtonGroup(); JRadioButton addButton=new JRadioButton( 并 ,false); buttonPanel.add(addButton); group.add(addButton); addButton.addActionListener(new ActionListener() public void actionPerformed(AetionEvent event) area=new Area(); area.add(area1); area.add(area2); panel.repaint(); ); JRadioButton subtractButton =new JRadioButton( 减 ,false); buttonPanel.add(subtractButton); group.add(subtractButton); subtractButton.addActionListener(new ActionListener() public void actionPerformed(ActionEvent event) area=new Area(); area.add(area1); area.subTract(area2); panel.repaint(); ); JRadioButton intersectButton =new JRadioButton( 交 ,false); buttonPanel.add(intersectButton); group.add(intersectButton); intersectButton.addActionListener(new ActionListener() public void actionPerformed(ActionEvent event) area=new Area(); area.add(area1); area.interseet(area2); panel.repaint(); ); JRadioButton exclusiveOrButton =new JRadioButton( 异或 ,false); buttonPanel.add(exclusiveOrButton); group.add(exclusiveOrButton); exclusiveOrButton.addActionListener(new ActionListener() public void actionPerformed(ActionEvent event) area=new Area(); area.add(area1); area.exclusiveor(area2); panel.repaint(); ); contentPane.add(buttonPanel,BorderLayout.NORTH); private JPanel panel; private Area area; private Area area1; private Area area2; private static final int WIDTH=400; private static final int HEIGHT=400;
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问答题
本题的功能是监听键盘敲击事件,并将敲击的字符显示在标签上。开始,文字标签提示“Please press your keyboard!”,当按下键盘上的字符键,文字标签就变为“’*’is pressed!”(*为所按字母)。 import java.awt.*; import java.awt.event.*; import javax.swing.*; public class java2 extends Frame______ public static void main(String args[]) java2 f=new java2( java2 ); Panel pan=new Panel(); f.init(); public java2(String str) super(str); public void init() addWindowListener(new WindowAdapter() public void windowClosing(WindowEvent e) System.exit(0); ); setSize(200,200); setLayout(new FlowLayout()); lab=new Label( Please press your keyboard! ); add(lab); addKeyListener(this); setVisible(true); public void keyTyped(KeyEvent e) lab.setText( ’ +______+ ’is pressed! ); repaint(); public void keyPressed(KeyEvent e) public void keyReleased(KeyEvent e) private Label lab;
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