Java Graphics怎么实现界面显示文字并换行

 public class Main {
    
    public  static void main(String[] strings)
    {
        String poem = "破阵子·为陈同甫赋壮词以寄之\r\n"
        + "作者：辛弃疾\r\n"
        + "\r\n"
        + "醉里挑灯看剑，梦回吹角连营。八百里分麾下炙，五十弦翻塞外声，沙场秋点兵。\r\n"
        + "马作的卢飞快，弓如霹雳弦惊。了却君王天下事，赢得生前身后名。可怜白发生！";
 
        AlgoFrame frame = new AlgoFrame("Java",poem, 600, 600);
        System.out.print("行路难，行路难，多歧路，今安在？\n"
                + "醉里挑灯看剑，梦回吹角连营");
    }
}

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Rectangle2D;
 
import javax.swing.*;
 
public class AlgoFrame extends JFrame {
    private int canvasWidth;
    private int canvasHeight;
    public AlgoFrame(String title, String poem, int canvasWidth, int canvasHeight){
 
        super(title);
 
        this.canvasHeight = canvasHeight;
        this.canvasWidth = canvasWidth;
 
 
//        AlgoCanvas canvas = new AlgoCanvas();
        AlgoCanvas canvas = new AlgoCanvas(poem);
        
        setContentPane(canvas);
        pack();
                
        setResizable(false);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
    }
 
    public AlgoFrame(String title){
        this(title, "", 1024, 768);
    }
 
 
    public int getCanvasWidth(){return  canvasWidth;}
    public int setCanvasHeight() {return canvasHeight;}
 
    private class AlgoCanvas extends JPanel{
        
        Font pf = new Font("Helvetica", Font.BOLD,20);
        String poem = "";
        
//        String poem = "破阵子·为陈同甫赋壮词以寄之\r\n"
//                + "作者：辛弃疾\r\n"
//                + "\r\n"
//                + "醉里挑灯看剑，梦回吹角连营。八百里分麾下炙，五十弦翻塞外声，沙场秋点兵。\r\n"
//                + "马作的卢飞快，弓如霹雳弦惊。了却君王天下事，赢得生前身后名。可怜白发生！";
        
        public AlgoCanvas (String strs) {
            this.poem = strs;
        }
    
        
        @Override
        public void paintComponent(Graphics gra) {
            
            Graphics2D graphics2d = (Graphics2D)gra;
            int strokeWidth = 5;
            graphics2d.setStroke(new BasicStroke(strokeWidth));
            
            graphics2d.setColor(Color.RED);
            Ellipse2D circle = new Ellipse2D.Double(60, 60, 300, 300);
            graphics2d.draw(circle);
            
            graphics2d.setColor(Color.BLACK);
            Rectangle2D rect = new Rectangle2D.Double(50, 50, 320, 320);
            graphics2d.draw(rect);
            
            graphics2d.setColor(Color.blue);
            Ellipse2D circle2 = new Ellipse2D.Float(80, 80, 260, 260);
//            graphics2d.draw(circle2);
            graphics2d.fill(circle2);
            
            
//            显示辛弃疾的词
            graphics2d.setColor(Color.black);
//            graphics2d.setFont(pf);
//            graphics2d.drawString(poem, 10, canvasHeight-100);
            
            drawStringWithFontStyleLineFeed(graphics2d,poem, 10, canvasHeight-100, pf);
            
        }
        
        @Override
        public Dimension getPreferredSize() {
//            System.out.println("running");
            return new Dimension(canvasWidth, canvasHeight);
        }
        
        
        //字符串总宽度
        private int  getStringLength(Graphics g, String str) {
            char[]  strcha=str.toCharArray();
            int strWidth = g.getFontMetrics().charsWidth(strcha, 0, str.length());
            System.out.println("字符总宽度:"+strWidth);
            return strWidth;
        }
        
        
//        //每一行字符串宽度  自定义  也就是画布中一行的宽度
//        int rowWidth=1110;  
//        //字符串字符的个数 
//        int strnum= str.length();
//        //每一行字符的个数
        
        private int getRowStrNum(int strnum,int rowWidth,int strWidth)
        {
            int rowstrnum=0;
            rowstrnum=(rowWidth*strnum)/strWidth;
            System.out.println("每行的字符数:"+rowstrnum);
            return rowstrnum;
        }
        
        //字符行数
        private  int  getRows(int strWidth,int rowWidth){
            int rows=0;
            if(strWidth%rowWidth>0){
                rows=strWidth/rowWidth+1;
            }else{
                rows=strWidth/rowWidth;
            }
            System.out.println("行数:"+rows);
            return rows;
        }
        
        //字符高度
        private int  getStringHeight(Graphics g) {
            int height = g.getFontMetrics().getHeight();
            System.out.println("字符高度:"+height);
            return height;
        }
        
//        注意设置font 才能计算宽度和高度
//        开始绘制
        private  void  drawStringWithFontStyleLineFeed(Graphics g, String strContent, int loc_X, int loc_Y, Font font)
        {
            g.setFont(font);
            
            //获取字符串 字符的总宽度
            int strWidth = getStringLength(g,strContent);
            
            //每一行字符串宽度
            int rowWidth = 500;
            System.out.println("每行字符宽度:"+rowWidth);
            
            //获取字符高度
            int strHeight=getStringHeight(g);
            
            //字符串总个数
            System.out.println("字符串总个数:"+strContent.length());
            if(strWidth>rowWidth){
                
                int rowstrnum=getRowStrNum(strContent.length(),rowWidth,strWidth);
                int  rows= getRows(strWidth,rowWidth);
                
                String temp="";
                for (int i = 0; i < rows; i++) {
                    //获取各行的String 
                    if(i==rows-1){
                        //最后一行
                        temp=strContent.substring(i*rowstrnum,strContent.length());
                    }else{
                        temp=strContent.substring(i*rowstrnum,i*rowstrnum+rowstrnum);
                    }
                    if(i>0){
                        //第一行不需要增加字符高度，以后的每一行在换行的时候都需要增加字符高度
                        loc_Y=loc_Y+strHeight;
                    }
                    g.drawString(temp, loc_X, loc_Y);
                }
            }else{
                //直接绘制
                g.drawString(strContent, loc_X, loc_Y);
            }
            
        }
    }
 
}