使用 java.awt.Graphics2D 画线，java.awt.graphics2d,使用 java.awt.

使用 java.awt.Graphics2D 画线，java.awt.graphics2d,使用 java.awt.

使用 java.awt.Graphics2D 画线，需要使用Line2D.Float方法，该方法的四个参数分别为起点的坐标x，y和终点的坐标x，y

public void paint(Graphics g) {        Graphics2D g2 = (Graphics2D) g;        Line2D lin = new Line2D.Float(100, 100, 250, 260);        g2.draw(lin);    }

下面是完整的代码：

import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.geom.Line2D;/** * Displays a JFrame and draws a line 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 line is drawn.     *     * @param g The graphics object     */    public void paint(Graphics g) {        Graphics2D g2 = (Graphics2D) g;        Line2D lin = new Line2D.Float(100, 100, 250, 260);        g2.draw(lin);    }    // <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);            }        });    }}