我是根據(jù)書上關于MVC結構的示例改寫成商品結賬系統(tǒng)的，書上的示例運行后的窗口如下圖。（接下來，我放的東西有點多，額。。算是一個仿寫代碼的過程吧，看了以后可以防雷吧）書上的示例代碼如下：Example10_15.java? public?class?Example10_15?{ ???public?static?void?main(String?args[]){ ??????WindowTriangle?win?=?new?WindowTriangle(); ??????win.setTitle("使用MVC結構");? ??????win.setBounds(100,100,420,260); ???} } WindowTriangle.java? import?java.awt.*; import?java.awt.event.*; import?javax.swing.*; public?class?WindowTriangle?extends?JFrame?implements?ActionListener?{ ???Triangle?triangle;?????????????//模型 ???JTextField?textA,textB,textC;???//視圖 ???JTextArea?showArea;?????????//視圖 ???JButton?controlButton;????????//控制器 ???WindowTriangle()?{ ??????init(); ??????setVisible(true); ??????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ???} ???void?init()?{ ?????triangle?=?new?Triangle(); ?????textA?=?new?JTextField(5);??? ?????textB?=?new?JTextField(5); ?????textC?=?new?JTextField(5); ?????showArea?=?new?JTextArea();???? ?????controlButton=new?JButton("計算面積"); ?????JPanel?pNorth=new?JPanel(); ?????pNorth.add(new?JLabel("邊A:")); ?????pNorth.add(textA); ?????pNorth.add(new?JLabel("邊B:")); ?????pNorth.add(textB); ?????pNorth.add(new?JLabel("邊C")); ?????pNorth.add(textC);? ?????pNorth.add(controlButton);? ?????controlButton.addActionListener(this); ?????add(pNorth,BorderLayout.NORTH); ?????add(new?JScrollPane(showArea),BorderLayout.CENTER); ???} ???public?void?actionPerformed(ActionEvent?e)?{ ?????try{?? ????????double?a?=?Double.parseDouble(textA.getText().trim());??? ????????double?b?=?Double.parseDouble(textB.getText().trim());?????? ????????double?c?=?Double.parseDouble(textC.getText().trim());? ????????triangle.setA(a)?;??????????//更新數(shù)據(jù) ????????triangle.setB(b); ????????triangle.setC(c); ????????String?area?=?triangle.getArea();????? ????????showArea.append("三角形"+a+","+b+","+c+"的面積:");? ????????showArea.append(area+"\n");??//更新視圖 ?????}? ?????catch(Exception?ex)?{ ????????showArea.append("\n"+ex+"\n"); ?????} ???} } Triangle.java? public?class?Triangle?{ ???double?sideA,sideB,sideC,area; ???boolean?isTriange; ???public?String?getArea()?{ ?????if(isTriange)?{ ????????double?p?=?(sideA+sideB+sideC)/2.0; ????????area?=?Math.sqrt(p*(p-sideA)*(p-sideB)*(p-sideC))?; ????????return?String.valueOf(area); ?????} ?????else?{? ????????return?"無法計算面積"; ?????} ???}? ???public?void?setA(double?a)?{ ?????sideA?=?a; ?????if(sideA+sideB>sideC&&sideA+sideC>sideB&&sideC+sideB>sideA)? ???????isTriange?=?true; ?????else? ???????isTriange?=?false; ???} ???public?void?setB(double?b)?{ ?????sideB?=?b; ?????if(sideA+sideB>sideC&&sideA+sideC>sideB&&sideC+sideB>sideA)? ???????isTriange?=?true; ?????else? ???????isTriange?=?false; ???} ???public?void?setC(double?c)?{ ?????sideC?=?c; ?????if(sideA+sideB>sideC&&sideA+sideC>sideB&&sideC+sideB>sideA)? ???????isTriange?=?true; ?????else? ???????isTriange?=?false; ???} }我自己改編的代碼如下：//Example10_15.java public?class?Example10_15 { public?static?void?main(String?args[]) { ??????WindowStringBuffer?win?=?new?WindowStringBuffer(); ??????win.setTitle("使用MVC結構");? ??????win.setBounds(100,100,420,260); } } //WindowStringBuffer.java? import?java.awt.*; import?java.awt.event.*; import?javax.swing.*; public?class?WindowStringBuffer?extends?JFrame?implements?ActionListener? { StringBuffer?stringBuffer;?????????????//模型 ???JTextField?textA,textB,textC,textD,textF;???//視圖 ???JTextArea?showArea?;?????????//視圖 ???JButton?controlButton;????????//控制器 ??? ???WindowStringBuffer()? ???{ ??????init(); ??????setVisible(true); ??????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ???} ??? ???void?init()? ???{ ?stringBuffer?=?new?StringBuffer(); ?????textA?=?new?JTextField(5);??? ?????textB?=?new?JTextField(5); ?????textC?=?new?JTextField(5); ?????textD?=?new?JTextField(5); ?????textF?=?new?JTextField(5); ????? ?????showArea?=?new?JTextArea();???? ?????controlButton=new?JButton("錄入商品信息"); ????? ?????JPanel?pNorth=new?JPanel(); ?????pNorth.add(new?JLabel("商品編號:")); ?????pNorth.add(textA); ?????pNorth.add(new?JLabel("商品名稱:")); ?????pNorth.add(textB); ?????pNorth.add(new?JLabel("商品產(chǎn)地：")); ?????pNorth.add(textC);? ?????pNorth.add(new?JLabel("商品單價：")); ?????pNorth.add(textD);? ?????pNorth.add(new?JLabel("商品數(shù)量：")); ?????pNorth.add(textF);? ????? ?????pNorth.add(controlButton);? ?????controlButton.addActionListener(this);??//設置監(jiān)視器 ?????add(pNorth,BorderLayout.NORTH); ?????add(new?JScrollPane(showArea),BorderLayout.CENTER); ???} ??? ???public?void?actionPerformed(ActionEvent?e)?//動作執(zhí)行 ???{ ?????try{?? ???? int?a?=?int.parseInt(textA.getText().trim());??? ????????String?b?=?String.parseString(textB.getText().trim());?????? ????????String?c?=?String.parseString(textC.getText().trim());? ????????double?d?=?Double.parseDouble(textD.getText().trim()); ????????int?f?=?int.parseInt(textF.getText().trim()); ???????? ????????stringBuffer.setGoodNum(a);??????????//更新數(shù)據(jù) ????????stringBuffer.setGoodName(b); ????????stringBuffer.setGoodArea(c); ????????stringBuffer.setGoodValue(d); ????????stringBuffer.setGoodSum(f); ???????? ????????String?information?=?stringBuffer.showInformation();????? ????????showArea.append("商品編號:"+a+","+"商品名稱:"+b+","+"商品產(chǎn)地:"+c+","+"商品價格:"+d+","+"商品數(shù)量:"+f);? ????????showArea.append(information+"\n");??//更新視圖 ?????}? ?????catch(Exception?ex)? ?????{ ????????showInformation.append("\n"+ex+"\n"); ?????} ???} } //StringBuffer.java public?class?StringBuffer? { int?goodNum,goodSum; double?goodValue; ????String?goodName,goodArea; ??? ???public?String?getInformation()? ???{ ?????stringBuffer.showInformation(); ??? ???public??setGoodNum(int?a) ???{ ???goodNum?=?a; ???????return?a; ???} ??? ???public??setGoodName(string?b) ???{ ???goodName?=?b; ???????return?b; ???} ??? ???public??setGoodArea(string?c) ???{ ???goodArea=?c; ???????return?c; ???} ??? ???public??setGoodValue(double?d) ???{ ???goodValue?=?d; ???????return?d; ???} ??? ???public??setGoodSum(int?f) ???{ ???goodSum?=?f; ???????return?f; ???} }心痛2017....我不知道我改的代碼錯在哪。。。難道顯示商品屬性不能用StringBuffer類做嗎？！！請大神指教也歡迎小伙伴前來討論！