《Java语言程序设计》第二套题答案

《Java语言程序设计》第二套题答案第二套题一、简答题1什么是多态性?方法的重载和覆盖有何区别?阅读下列代码，指出其中存在的重载和覆盖，写出输出结果是什么？解释为什么这样输出?(15分)classClass1{ publicvoidfind(){ System.out.println("Class1.find"); }}classClass2extendsClass1{ publicvoidfind(){ System.out.println("Class2.find"); }}classClass3{ publicvoidget(Class1one){ System.out.println("get(Class1)"); one.find(); } publicvoidget(Class2two){ System.out.println("get(Class2)"); two.find(); }}publicclassTest1{ publicstaticvoidmain(String[]args) { Class1one=newClass2(); Class3three=newClass3(); three.get(one); }}get(Class1)Class2.find多态：就是父类引用可以持有子类对象。这时候只能调用父类中的方法，而子类中特有方法是无法访问的，因为这个时候（编译时）你把他看作父类对象的原因，但是到了运行的时候，编译器就会发现这个父类引用中原来是一个子类的对像，所以如果父类和子类中有相同的方法时，调用的会是子类中的方法，而不是父类的。

方法重载是让类以统一的方式处理不同类型数据的一种手段。多个同名函数同时存在，具有不同的参数个数/类型。覆盖方法的签名完全相同，但函数体不同Class2继承Class1其中Class2对Class1find方法进行了覆盖Class3中对get方法进行了重载输出如上结果是因为多态，调用的是Class1的find方法。2、请说说final、finally的区别和作用，举例说明用法；另外用自己的语言介绍throw/throws有什么联系和区别？在程序中应如何使用？(15分)final是全局变量声明的时候使用，意思是这个变量不可被修改，不可被override，一般用于声明常量，或者系统设置的值。finally是在try-catch-finally块中配套使用，作用是，不管代码执行了try还是catch，最后一定会执行finally里面的代码如：方法finalvoidf(){System.out.println("dddd");}属性finalintaa;try{

}catch(Exceptione){

}finally{//一定会执行的代码

}3、编写一个描述老师基本情况的类，属性包括姓名，教工号，基本工资，岗位工资和绩效工资，方法包括信息输出，设置姓名和教工号，设置三种工资金额，计算总工资(三种工资加起来)和税后工资(按如下方式计算，3000以内不收税，3000-5000之间的部分扣10%，大于5000的部分扣15%)。在main方法中对方法进行测试(15分)publicclassTestTeacher{staticclassT{privateStringxingming;privateStringjiaogonghao;privatefloatjibengongzhi;privatefloatgangweigongzhi;privatefloatjixiao;publicStringgetXingming(){returnxingming;}publicvoidsetXingming(Stringxingming){this.xingming=xingming;}publicStringgetJiaogonghao(){returnjiaogonghao;}publicvoidsetJiaogonghao(Stringjiaogonghao){this.jiaogonghao=jiaogonghao;}publicfloatgetJibengongzhi(){returnjibengongzhi;}publicvoidsetJibengongzhi(floatjibengongzhi){this.jibengongzhi=jibengongzhi;}publicfloatgetGangweigongzhi(){returngangweigongzhi;}publicvoidsetGangweigongzhi(floatgangweigongzhi){this.gangweigongzhi=gangweigongzhi;}publicfloatgetJixiao(){returnjixiao;}publicvoidsetJixiao(floatjixiao){this.jixiao=jixiao;}publicfloatzhonggongzhi(){returnjibengongzhi+gangweigongzhi+jixiao;}publicfloatshuihougongzhi(){floatzhonggongzhi;zhonggongzhi=zhonggongzhi();if(zhonggongzhi<3000){returnzhonggongzhi;}elseif(zhonggongzhi>=3000&&zhonggongzhi<5000){returnzhonggongzhi-(zhonggongzhi-3000)*0.1f;}elseif(zhonggongzhi>=5000){returnzhonggongzhi-(zhonggongzhi-3000)*0.15f;}return-1;}}publicstaticvoidmain(String[]args){Tteacher=newT();teacher.setXingming("klo");teacher.setJiaogonghao("1230000");teacher.setJibengongzhi(1000);teacher.setGangweigongzhi(1000);teacher.setJixiao(1000);System.out.println("zhonggongzhi:"+teacher.zhonggongzhi());System.out.println("shuihougongzhi:"+teacher.shuihougongzhi());}}4、Java中实现多线程有几种方式？这几种方式有什么区别？然后采取其中一种方式设计一个线程例子，在例子中构造4个线程对象实现对同一数据类对象进行操作(数据初始值为10)，其中线程对象1对数据执行乘以10的操作，线程对象2对数据执行乘以20的操作,对象3对数据执行+30的操作，线程对象4对数据执行+40的操作，要求考虑线程同步，保证每一步数据操作的正确性。要求提供程序代码以及运行结果截图（15分)答：常用的方式有1、继承Thread类实现方法run()不可以抛异常无返回值2、实现Runnable接口实现Runnable接口实现方法run()不可以抛异常无返回值3、线程池线程由线程池提交，管理importstaticjava.lang.Thread.sleep;importjava.util.concurrent.ExecutorService;importjava.util.concurrent.Executors;importjava.util.logging.Level;importjava.util.logging.Logger;publicclassTestExecutor{intnumber=10;publicstaticvoidmain(String[]ss){finalTestExecutortestExecutor=newTestExecutor();testExecutor.test();}publicvoidtest(){ExecutorServicecachedThreadPool=Executors.newCachedThreadPool();cachedThreadPool.execute(newRunnableImpl());cachedThreadPool.execute(newRunnableImpl1());cachedThreadPool.execute(newRunnableImpl2());cachedThreadPool.execute(newRunnableImpl3());}publicvoidxiugai(intthreadType){synchronized(this){switch(threadType){case0:number=number*10;break;case1:number=number*20;break;case2:number=number+30;break;case3:number=number+40;break;default:break;}System.out.println(Thread.currentThread().getName()+"："+number);}}privateclassRunnableImplimplementsRunnable{publicRunnableImpl(){}@Overridepublicvoidrun(){try{while(true){xiugai(0);sleep(3000);}}catch(InterruptedExceptionex){Logger.getLogger(TestExecutor.class.getName()).log(Level.SEVERE,null,ex);}}}privateclassRunnableImpl1implementsRunnable{publicRunnableImpl1(){}@Overridepublicvoidrun(){try{while(true){xiugai(1);sleep(3000);}}catch(InterruptedExceptionex){Logger.getLogger(TestExecutor.class.getName()).log(Level.SEVERE,null,ex);}}}privateclassRunnableImpl2implementsRunnable{publicRunnableImpl2(){}@Overridepublicvoidrun(){try{while(true){xiugai(2);sleep(3000);}}catch(InterruptedExceptionex){Logger.getLogger(TestExecutor.class.getName()).log(Level.SEVERE,null,ex);}}}privateclassRunnableImpl3implementsRunnable{publicRunnableImpl3(){}@Overridepublicvoidrun(){try{while(true){xiugai(3);sleep(3000);}}catch(InterruptedExceptionex){Logger.getLogger(TestExecutor.class.getName()).log(Level.SEVERE,null,ex);}}}}二、编程题1、编写一个图形用户界面程序，包含两个按钮，一个信息标签（label）和一个显示面板，两个按钮分别为“掷色子”和“移动”，在显示面板中显示一个小汽车（用小圆\矩形以及线绘制），随机设定小汽车的初始位置，当点击“掷色子”按钮，随机产生移动信息（上移，下移，左移，右移，移动几步）,并显示在信息标签中，点击移动，按照产生的移动信息，让小汽车进行移动。要求提供完整程序代码以及运行结果截图（20分)importjava.awt.Graphics;importjava.util.Random;publicclassmainextendsjavax.swing.JFrame{intx=100;inty=50;intrandomNum=0;intrandomPosition=0;String[]strs={"上移","下移","左移","右移"};publicmain(){initComponents();}@SuppressWarnings("unchecked")//<editor-folddefaultstate="collapsed"desc="GeneratedCode">privatevoidinitComponents(){jButton1=newjavax.swing.JButton();jButton2=newjavax.swing.JButton();jLabel1=newjavax.swing.JLabel();setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);getContentPane().setLayout(newjava.awt.GridBagLayout());jButton1.setText("掷色子");jButton1.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jButton1ActionPerformed(evt);}});getContentPane().add(jButton1,newjava.awt.GridBagConstraints());jButton2.setText("移动");jButton2.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jButton2ActionPerformed(evt);}});getContentPane().add(jButton2,newjava.awt.GridBagConstraints());getContentPane().add(jLabel1,newjava.awt.GridBagConstraints());pack();}//</editor-fold>privatevoidjButton1ActionPerformed(java.awt.event.ActionEventevt){Randomrandom=newRandom();randomNum=random.nextInt(4)+1;randomPosition=random.nextInt(4);jLabel1.setText(strs[randomPosition]+randomNum+"步");}privatevoidjButton2ActionPerformed(java.awt.event.ActionEventevt){repaint();}publicstaticvoidmain(Stringargs[]){try{for(javax.swing.UIManager.LookAndFeelInfoinfo:javax.swing.UIManager.getInstalledLookAndFeels()){if("Nimbus".equals(info.getName())){javax.swing.UIManager.setLookAndFeel(info.getClassName());break;}}}catch(ClassNotFoundException|InstantiationException|IllegalAccessException|javax.swing.UnsupportedLookAndFeelExceptionex){java.util.logging.Logger.getLogger(main.class.getName()).log(java.util.logging.Level.SEVERE,null,ex);}//</editor-fold>//</editor-fold>/*Createanddisplaytheform*/java.awt.EventQueue.invokeLater(newRunnableImpl());}@Overridepublicvoidpaint(Graphicsg){super.paint(g);switch(randomPosition){case0:y=y-randomNum*15;break;case1:y=y+randomNum*15;break;case2:x=x-randomNum*15;break;case3:x=x+randomNum*15;break;default:break;}g.drawRect(x,y,40,40);}//Variablesdeclaration-donotmodifyprivatejavax.swing.JButtonjButton1;privatejavax.swing.JButtonjButton2;privatejavax.swing.JLabeljLabel1;//EndofvariablesdeclarationprivatestaticclassRunnableImplimplementsRunnable{publicRunnableImpl(){}@Overridepublicvoidrun(){newmain().setVisible(true);}}}2、编写一个班级推优（三好生）投票管理程序。列出参与推优的学生名单（8名），可以勾选进行投票，要求每个参选学生前面有图标表示候选人的性别，每人可以投4名候选人，每次投票后能够显示当前投票人数以及每名候选者得票数，图形化柱状图显示得票数，可以保存投票结果到文本文件。要求提供完整程序代码以及运行结果截图(20分)/**Tochangethislicenseheader,chooseLicenseHeadersinProjectProperties.*Tochangethistemplatefile,chooseTools|Templates*andopenthetemplateintheeditor.*/packagetestjava;importjava.awt.BorderLayout;importjava.awt.Font;importjava.util.List;importjavax.swing.JCheckBox;importorg.jfree.chart.ChartFactory;importorg.jfree.chart.ChartPanel;importorg.jfree.chart.JFreeChart;importorg.jfree.chart.axis.CategoryAxis;importorg.jfree.chart.axis.NumberAxis;importorg.jfree.chart.axis.ValueAxis;importorg.jfree.chart.plot.CategoryPlot;importorg.jfree.chart.plot.PlotOrientation;importorg.jfree.data.category.CategoryDataset;importorg.jfree.data.category.DefaultCategoryDataset;/****@authorldl*/publicclassTestFr1extendsjavax.swing.JFrame{privatejavax.swing.JButtonjButton1;privatejavax.swing.JCheckBoxjCheckBox1;privatejavax.swing.JCheckBoxjCheckBox2;privatejavax.swing.JCheckBoxjCheckBox3;privatejavax.swing.JCheckBoxjCheckBox4;privatejavax.swing.JCheckBoxjCheckBox5;privatejavax.swing.JCheckBoxjCheckBox6;privatejavax.swing.JPaneljPanel1;/***CreatesnewformTestFr*/publicTestFr1(){initComponents();CategoryDatasetdataset=getDataSet();JFreeChartchart=ChartFactory.createBarChart("统计",//图表标题"投票统计",//目录轴的显示标签"数量",//数值轴的显示标签dataset,//数据集PlotOrientation.VERTICAL,//图表方向：水平、垂直true,false,false);CategoryPlotplot=chart.getCategoryPlot();//获取图表区域对象NumberAxisnumberaxis=(NumberAxis)plot.getRangeAxis();numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());CategoryAxisdomainAxis=plot.getDomainAxis();//水平底部列表domainAxis.setLabelFont(newFont("黑体",Font.BOLD,14));//水平底部标题domainAxis.setTickLabelFont(newFont("宋体",Font.BOLD,12));//垂直标题ValueAxisrangeAxis=plot.getRangeAxis();//获取柱状rangeAxis.setLabelFont(newFont("黑体",Font.BOLD,15));chart.getLegend().setItemFont(newFont("黑体",Font.BOLD,15));chart.getTitle().setFont(newFont("宋体",Font.BOLD,20));//设置标题字体ChartPanelchartPanel=newChartPanel(chart,true);jPanel1.setLayout(newBorderLayout(0,0));jPanel1.add(chartPanel);jPanel1.repaint();}/***Thismethodiscalledfromwithintheconstructortoinitializetheform.*WARNING:DoNOTmodifythiscode.Thecontentofthismethodisalways*regeneratedbytheFormEditor.*/@SuppressWarnings("unchecked")//<editor-folddefaultstate="collapsed"desc="GeneratedCode">//GEN-BEGIN:initComponentsprivatevoidinitComponents(){jCheckBox1=newjavax.swing.JCheckBox();jPanel1=newjavax.swing.JPanel();jCheckBox5=newjavax.swing.JCheckBox();jCheckBox2=newjavax.swing.JCheckBox();jCheckBox3=newjavax.swing.JCheckBox();jCheckBox6=newjavax.swing.JCheckBox();jCheckBox4=newjavax.swing.JCheckBox();jButton1=newjavax.swing.JButton();setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);jCheckBox1.setText("班长");jCheckBox1.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jCheckBox1ActionPerformed(evt);}});javax.swing.GroupLayoutjPanel1Layout=newjavax.swing.GroupLayout(jPanel1);jPanel1.setLayout(jPanel1Layout);jPanel1Layout.setHorizontalGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGap(0,411,Short.MAX_VALUE));jPanel1Layout.setVerticalGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGap(0,0,Short.MAX_VALUE));jCheckBox5.setText("大山4");jCheckBox5.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jCheckBox5ActionPerformed(evt);}});jCheckBox2.setText("卫生1");jCheckBox2.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jCheckBox2ActionPerformed(evt);}});jCheckBox3.setText("大山2");jCheckBox3.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jCheckBox3ActionPerformed(evt);}});jCheckBox6.setText("大山5");jCheckBox6.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jCheckBox6ActionPerformed(evt);}});jCheckBox4.setText("大山3");jCheckBox4.addActionListener(newjava.awt.event.ActionListener(){publicvoidactionPerformed(java.awt.event.ActionEventevt){jCheckBox4ActionPerformed(evt);}});jButton1.setText("投票");javax.swing.GroupLayoutlayout=newjavax.swing.GroupLayout(getContentPane());getContentPane().setLayout(layout);layout.setHorizontalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(layout.createSequentialGroup().addContainerGap().addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addComponent(jCheckBox1).addComponent(jCheckBox2).addComponent(jCheckBox3).addComponent(jCheckBox4).addComponent(jCheckBox5).addComponent(jCheckBox6).addComponent(jButton1)).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addComponent(jPanel1,javax.swing.GroupLayout.DEFAULT_SIZE,javax.swing.GroupLayout.DEFAULT_SIZE,Short.MAX_VALUE)));layout.setVerticalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(layout.createSequentialGroup().addGap(14,14,14).addComponent(jCheckBox1).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED).addComponent(jCheckBox2).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addComponent(jCheckBox3).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED).addComponent(jCheckBox4).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED).addComponent(jCheckBox5).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED).addComponent(jCheckBox6).addGap(18,18,18).addComponent(jButton1).addContainerGap(83,Short.MAX_VALUE)).addComponent(jPanel1,javax.swing.GroupLayout.DEFAULT_SIZE,javax.swing.GroupLayout.DEFAULT_SIZE,Short.MAX_VALUE));pack();}//</editor-fold>//GEN-END:initComponents/***@paramargsthecommandlinearguments*/publicstaticvoidmain(Stringargs[]){/*SettheNimbuslookandfeel*///<editor-folddefaultstate="collapsed"desc="Lookandfeelsettingcode(optional)">/*IfNimbus(introducedinJavaSE6)isnotavailable,staywiththedefaultlookandfeel.*Fordetailssee/javase/tutorial/uiswing/lookandfeel/plaf.html*/try{for(javax.swing.UIManager.LookAndFeelInfoinfo:javax.swing.UIManager.getInstalledLookAndFeels()){if("Nimbus".equals(info.getName())){javax.swing.UIManager.setLookAndFeel(info.getClassName());break;}}}catch(ClassNotFoundExceptionex){java.util.logging.Logger.getLogger(TestFr.class.getName()).log(java.util.logging.Level.SEVERE,null,ex);}catch(InstantiationExceptionex){java.util.logging.Logger.getLogger(TestFr.class.getName()).log(java.util.logging.Level.SEVERE,null,ex);}catch(IllegalAccessExceptionex){java.util.logging.Logger.getLogger(TestFr.class.getName()).log(java.util.logging.Level.SEVERE,null,ex);}catch(javax.swing.UnsupportedLookAndFeelExceptionex){java.util.logging.Logger.getLogger(TestFr.class.getName()).log(java.util.logging.Level.SEVERE,null,ex);}//</editor-fold>/*Createanddisplaytheform*/java.awt.EventQueue.invokeLater(newRunnable(){publicvoidrun(){newTestFr().setVisible(true);}});} privatevoidjCheckBox1ActionPerformed(java.awt.event.ActionEventevt){JCheckBoxjCheckBox=(JCheckBox)evt.getSource();intintValue=dataset.getValue(0,0).intValue();if(jCheckBox.isSelected()){intValue++;}else{intValue--;}dataset.setValue(intValue,"1","1");}privatevoidjCheckBox5ActionPerformed(java.awt.event.ActionEventevt){//TODOaddyourhandlingcodehere:JCheckBoxjCheckBox=(JCheckBox)evt.getSource();intintValue=dataset.getValue(4,4).intValue();if(jCheckBox.isSelected()){intValue++;}else{intValue--;}dataset.setValue(intValue,"4","4");}privatevoidjCheckBox2ActionPerformed(java.awt.event.ActionEventevt){