java新手代码大全实例 关于java入门基础知识(2)

java新手代码大全实例

同心圆：

import java.awt.*;import javax.swing.*; public class Circle99Frame extends JFrame { public static void main(String args[]) { JFrame frame=new Circle99Frame(); frame.setDefaultCloseOperation(DISPOSE_ON_CLOSE); frame.setSize(600,600); frame.setVisible(true); } public void paint( Graphics g) { g.drawString("circle 99",20,20); int x0=getSize().width/2; int y0=getSize().height/2; for(int r=0;r<getSize().height/2;r+=10) { g.setColor(getRandomColor()); g.drawOval(x0-r,y0-r,r*2,r*2); } } Color getRandomColor() { return new Color( (int)(Math.random()*255),//random本身只产生（0~1）之间的小数， (int)(Math.random()*255), (int)(Math.random()*255) ); }}

下面呢是一个常见的简陋的登陆界面，这个程序是这个两个类class共同组成的程序，先看代码：

import javax.swing.JFrame; import javax.swing.JPanel; public class DemoFrame extends JFrame{ public DemoFrame(DemoPanel panel) { this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.setSize(300, 200); this.setTitle("Frame Demo"); this.add(panel); this.setResizable(false); this.setVisible(true); } public static void main(String[] args) { DemoPanel panel = new DemoPanel(); DemoFrame Frame = new DemoFrame(panel); } }

import java.awt.GridLayout; import javax.swing.JButton; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JPasswordField; import javax.swing.JTextField; public class DemoPanel extends JPanel{ private JLabel labelUser, labelPassWd; //标签 用户名，密码 private JButton buttonLogin, buttonReset; //按钮 登录，重置 private JTextField textFieldUserName; //文本框 用户名输入 private JPasswordField passWdField; //密码框 密码输入 private JPanel panelUserName; private JPanel panelPassWd; private JPanel panelLoginButton; public DemoPanel(){ this.labelUser = new JLabel("用户名"); this.labelPassWd = new JLabel("密 码"); this.buttonLogin = new JButton("登录"); this.buttonReset = new JButton("重置"); this.textFieldUserName = new JTextField(10); this.passWdField = new JPasswordField(10); this.panelPassWd = new JPanel(); this.panelUserName = new JPanel(); this.panelLoginButton = new JPanel(); this.setLayout(new GridLayout(3, 1)); //网格式布局 this.panelUserName.add(this.labelUser); this.panelUserName.add(this.textFieldUserName); this.panelPassWd.add(this.labelPassWd); this.panelPassWd.add(this.passWdField); this.panelLoginButton.add(buttonLogin); this.panelLoginButton.add(buttonReset); this.add(this.panelUserName); this.add(this.panelPassWd); this.add(this.panelLoginButton); } }

程序结果如下 :

简单的加法器：

package TEST; import javax.swing.JOptionPane; //导入类 public class TEST { public static void main(String args[]) { String input_pane1,input_pane2; int n1,n2,sum; input_pane1 = JOptionPane.showInputDialog("Please input the first number"); //输入框1 input_pane2 = JOptionPane.showInputDialog("Please input the second number"); //输入框2 n1 = Integer.parseInt(input_pane1); //获取输入框中输入数据的整数类型 n2 = Integer.parseInt(input_pane2);//获取输入框中输入数据的整数类型 sum = n1+n2; JOptionPane.showMessageDialog(null, "The sum is: "+sum,"Adding Device",JOptionPane.PLAIN_MESSAGE); //第1个参数：null 显示在中央 //第2个参数：要显示的字符 //第3个参数：标题栏信息 //第4个参数：对话框类型 System.exit(0); //终结图形用户界面程序必须的 } }

结果如下: