java上机考试

1.产生n个30以内的随机数，统计并输出1,2,3，各数段的数的个数，并输出数中的最大数和最小数。

package com.zhang;import java.util.Random;import java.util.Scanner;public class Demo1 {public static void main(String[] args) {Scanner sc=new Scanner(System.in);int n=0,number;int arr[]=new int[31];int maxNum=0, minNum=0;System.out.println("请输入要产生的随机数的个数n:");n=sc.nextInt();for (int i = 0; i < n; i++) {Random r=new Random();int num=r.nextInt(31);arr[num]++;if(i==0){maxNum=minNum=num;}if(i>0){if(num>maxNum){maxNum=num;}if(num<minNum){minNum=num;}}}for (int i = 0; i < 31; i++) {System.out.println(i+"出现了"+arr[i]+"次");}System.out.println("产生的最大数是:"+maxNum);System.out.println("产生的最小数是:"+minNum);}}2定义一个接口，接口中有四个抽象方法：求面积方法、求周长方法、显示面积方法及显示周长方法。

定义Circle类和Rectangle类分别实现接口，在主类中实现显示圆和矩形的面积和周长。

package com.zhang;public interface Tuxing {public abstract void setArea();public abstract void setGrith();public abstract double getArea();public abstract double getGrith();}package com.zhang;public class Cricle implements Tuxing {double r, grith, area;// r表示半径.grith是周长,area是面积public Cricle(double r) {this.r = r;}@Overridepublic void setArea() {// TODO Auto-generated method stubarea=Math.PI*r*r;}@Overridepublic void setGrith() {// TODO Auto-generated method stubgrith=2*r*Math.PI;}@Overridepublic double getArea() {// TODO Auto-generated method stubreturn area;}@Overridepublic double getGrith() {// TODO Auto-generated method stubreturn grith;}}package com.zhang;public class Rectangle implements Tuxing { double height, width;double grith, area;public Rectangle(double height, double width) { this.height = height;this.width = width;}@Overridepublic void setArea() {// TODO Auto-generated method stubarea=height*width;}@Overridepublic void setGrith() {// TODO Auto-generated method stubgrith=2*(height+width);}@Overridepublic double getArea() {// TODO Auto-generated method stubreturn area;}@Overridepublic double getGrith() {// TODO Auto-generated method stubreturn grith;}}package com.zhang;public class CeShi {public static void main(String[] args) {Cricle cricle=new Cricle(2);Rectangle rectangle=new Rectangle(2, 2);cricle.setArea();cricle.setGrith();rectangle.setArea();rectangle.setGrith();System.out.println("圆的面积是"+cricle.getArea());System.out.println("圆的周长是"+cricle.getGrith());System.out.println("矩形的面积是"+rectangle.getArea());System.out.println("矩形的周长是"+rectangle.getGrith());}}3用户在两个输入框中分别输入两个整数，单击“求积”按钮，在第三个输入框中显示两数中的积，单击“求和”按钮，在第四个输入框中显示两数的和。

package com.zhang;import java.awt.BorderLayout;import java.awt.GridLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;import javax.swing.JTextField;public class Demo3 extends JFrame {JTextField tf1, tf2, tf3, tf4;public Demo3() {// TODO Auto-generated constructor stubsuper();setTitle("简单的计算GUI");setSize(250, 180);JPanel panel = new JPanel(new GridLayout(0, 2));JLabel label1 = new JLabel("第一个整数:");panel.add(label1);tf1 = new JTextField();panel.add(tf1);JLabel label2 = new JLabel("第二个整数:");panel.add(label2);tf2 = new JTextField();panel.add(tf2);JLabel label3 = new JLabel("积的结果:");panel.add(label3);tf3 = new JTextField();panel.add(tf3);JLabel label4 = new JLabel("和的结果:");panel.add(label4);tf4 = new JTextField();panel.add(tf4);getContentPane().add(panel, BorderLayout.NORTH);JPanel panel2 = new JPanel();JButton bu1 = new JButton("求积");bu1.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {// TODO Auto-generated method stubint ji = Integer.parseInt(tf1.getText().trim())* Integer.parseInt(tf2.getText().trim());tf3.setText(ji+"");}});panel2.add(bu1);JButton bu2 = new JButton("求和");bu2.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {// TODO Auto-generated method stubint he = Integer.parseInt(tf1.getText().trim())+ Integer.parseInt(tf2.getText().trim());tf4.setText(he+"");}});panel2.add(bu2);getContentPane().add(panel2, BorderLayout.SOUTH);setVisible(true);}public static void main(String[] args) {new Demo3();}}效果：4设计一个下拉式菜单和弹出式菜单，菜单标题为：设置窗体背景色。

菜单中包含4个选项：红色、绿色、蓝色、退出，快捷键如下图所示，并在“蓝色”与“退出”选项间加一条分隔线。

给菜单项注册事件监听器并完成相应的功能。

package com.zhang;import java.awt.Color;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.KeyEvent;import java.awt.event.MouseAdapter;import java.awt.event.MouseEvent;import javax.swing.JFrame;import javax.swing.JMenu;import javax.swing.JMenuBar;import javax.swing.JMenuItem;import javax.swing.JPopupMenu;import javax.swing.JTextArea;import javax.swing.KeyStroke;public class Demo4 extends JFrame implements ActionListener {JMenuBar menubar;JMenu menu;JMenuItem Item1, Item2, Item3, Item4, Item5, Item6, Item7, Item8;JPopupMenu popmenu;JTextArea textarea;public Demo4() {// TODO Auto-generated constructor stubsuper();setTitle("菜单例子");setSize(300, 200);menubar = new JMenuBar();setJMenuBar(menubar);menu = new JMenu("菜单");menubar.add(menu);Item1 = new JMenuItem("红色");Item1.setMnemonic(KeyEvent.VK_R);Item1.setAccelerator(KeyStroke.getKeyStroke('R', 2));// ctrl+r快捷键menu.add(Item1);Item2 = new JMenuItem("绿色");Item2.setMnemonic(KeyEvent.VK_G);Item2.setAccelerator(KeyStroke.getKeyStroke('G', 2));// ctrl+g快捷键menu.add(Item2);Item3 = new JMenuItem("蓝色");Item3.setMnemonic(KeyEvent.VK_B);Item3.setAccelerator(KeyStroke.getKeyStroke('B', 2));// ctrl+b快捷键menu.add(Item3);Item4 = new JMenuItem("退出");Item4.setMnemonic(KeyEvent.VK_E);Item4.setAccelerator(KeyStroke.getKeyStroke('E', 2));// ctrl+e快捷键menu.addSeparator();menu.add(Item4);Item1.addActionListener(this);Item2.addActionListener(this);Item3.addActionListener(this);Item4.addActionListener(this);// 创建文本区的菜单项Item5 = new JMenuItem("红色");Item6 = new JMenuItem("绿色");Item7 = new JMenuItem("蓝色");Item8 = new JMenuItem("退出");// 在文本区添加右键菜单textarea = new JTextArea();getContentPane().add(textarea);popmenu = new JPopupMenu();textarea.add(popmenu);textarea.addMouseListener(new MouseAdapter() {@Overridepublic void mouseClicked(MouseEvent e) {// TODO Auto-generated method stubif (e.getModifiers() == MouseEvent.BUTTON3_MASK) { popmenu.show(textarea, e.getX(), e.getY());}}});// 添加菜单项到右键菜单popmenu.add(Item5);popmenu.add(Item6);popmenu.add(Item7);popmenu.add(Item8);// 添加动作事件监听器Item5.addActionListener(this);Item6.addActionListener(this);Item7.addActionListener(this);Item8.addActionListener(this);setVisible(true);setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);setLocationRelativeTo(null);}@Overridepublic void actionPerformed(ActionEvent e) {// TODO Auto-generated method stubif (e.getSource() == Item1) {textarea.setBackground(Color.red);}if (e.getSource() == Item2) {textarea.setBackground(Color.green);}if (e.getSource() == Item3) {textarea.setBackground(Color.blue);}if (e.getSource() == Item4) {System.exit(0);}if (e.getSource() == Item5) {textarea.setBackground(Color.red);}if (e.getSource() == Item6) {textarea.setBackground(Color.green);}if (e.getSource() == Item7) {textarea.setBackground(Color.blue);}if (e.getSource() == Item8) {System.exit(0);}}public static void main(String[] args) {new Demo4();}}效果:5构造函数初始化为坐标原点，然后定义一个方法实现点的移动，再定义一个方法打印当前点的坐标。