使用java.awt.Graphics2D画矩形详解编程语言

java画矩形需要使用Rectangle2D.Float静态方法，指定四个参数即可，四个参数分别为左上角的xy坐标，以及矩形的宽度和高度

import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.geom.Rectangle2D; 
/** 
 * Displays a JFrame and draws a ractangle on it using the Java 2D Graphics API 
 * 
 * @author cn.outofmemory 
 */ 
public class Java2DFrame extends javax.swing.JFrame { 
 
    /** 
     * Creates a new instance of Java2DFrame 
     */ 
    public Java2DFrame() { 
        initComponents(); 
    } 
 
    /** 
     * This is the method where the rectangle is drawn. 
     * 
     * @param g The graphics object 
     */ 
    public void paint(Graphics g) { 
        Graphics2D graphics2 = (Graphics2D) g; 
        Rectangle2D rectangle = new Rectangle2D.Float(100, 100, 240, 160); 
        graphics2.draw(rectangle);  
    } 
 
    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">  
    private void initComponents() { 
 
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); 
        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane()); 
        getContentPane().setLayout(layout); 
        layout.setHorizontalGroup( 
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) 
            .add(0, 400, Short.MAX_VALUE) 
        ); 
        layout.setVerticalGroup( 
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) 
            .add(0, 300, Short.MAX_VALUE) 
        ); 
        pack(); 
    }// </editor-fold>  
 
    /** 
     * Starts the program 
     * 
     * @param args the command line arguments 
     */ 
    public static void main(String args[]) { 
        java.awt.EventQueue.invokeLater(new Runnable() { 
            public void run() { 
                new Java2DFrame().setVisible(true); 
            } 
        }); 
    } 
}