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1、Java上机实践三实验题目 1假设字符串 s1、s2、s3 的定义如下：String s1 = “A String ”;String s2 = “A String ”;String s3 = s1;请写出下列表达式的值：s1 = s2 s1 = s3 s1.length() s1.equals(s2) s1.equals(s3) pareTo(s2) pareTo(s3) s1.concat(s3) s1.indexOf(t ) s3.lastIndexOf( t ) 实验目的(1) 熟悉字符串类 String。(2) 学习创建类 String 的对象。(3) 学习使用类 String 执行字
2、符串操作。实验步骤(1) 按题目的要求创建 String 对象 s1、s2，并声明对象引用 s3 指向 s1；(2) 调用 String 类的相关方法，执行指定操作并输出结果。package lab1;public class Showstr public static void main(String args)String s1 =A String;String s2 =A String;String s3 = s1;= s2);= s3);实验 2 Java异常处理一、实验目的1) 掌握 Java异常的概念及工作机制 2) 掌握异常的分类3) 掌握抛出异常语句的使用 (throw)4)
3、掌握抛出捕获处理异常语句的使用 (try catch finally)5) 掌握上抛异常语句的使用 (throws)6) 掌握创建自定义异常二、实验环境JDK1.6+Eclpise3.2三、实验内容1、编写一个应用程序， 要求从键盘输入一个 double 型的圆的半径， 计算并输出其面积。 测试当输入的数据不是 double 型数据(如字符串“ abc”)会产生什么结果，怎样处理。package lab2;public class Err_1 public static void main(String args)Scanner reader=new Scanner(System.in);do
4、uble r;tryr=reader.nextDouble();catch(InputMismatchException e)数据类型错误 +e.toString();2、计算两个正数之和，当任意一个数超出范围时，抛出自己定义的异常 ( NumberRangeException )。package lab2;class NumberRangeException extends ExceptionNumberRangeException(String msg) super(msg); public class Err_2 public static void main(String args)S
5、canner reader=new Scanner(System.in);tryint a=reader.nextInt();int b=reader.nextInt(); if(a=0|b=0)NumberRangeException e=new NumberRangeException(The number beyond range!);throw e; 实验 3 输入和输出1实验目的 了解流式输入输出的基本原理；掌握类File、 FileInputStream 、FileOutputStream 的使用方法。2实验内容 ( 1)编程：检查 C:WINDOWSsetuplog.txt 文件
6、是否存在，若在则显示该文 件的名称和内容。package lab3;public class Inoutprivate static Scanner in;public static void main(String args)throws IOExceptiontryFile f1=new File(C:WINDOWSsetuplog.txt);in = new Scanner(new File(C:WINDOWSsetuplog.txt);while (in.hasNextLine() String str = catch(IOException e)(2)编程：输入 5 个学生的信息(包
7、含学号、姓名、 3科成绩)，统计各学生的总分，然后 将学生信息和统计结果存入二进制数据文件STUDENT.DAT中。 3实验要求 编程时，应考虑异常处理。package lab3;class StudentString snum;String name;int a,b,c,sum;public void Info()Scanner reader=new Scanner(System.in);b=reader.nextInt();c=reader.nextInt();sum=a+b+c;reader.close();public class Inout_2public static void m
8、ain(String args)throws IOExceptiontryFileOutputStream raf=new FileOutputStream(dari.txt,true); ObjectOutputStream out=new ObjectOutputStream(raf);Student stu=new Student5;for(int i=0;i5;i+) stui=new Student(); (stui).Info(); out.writeObject(stui);out.close();catch(IOException ioe)catch(Exception e)实
9、验题目 4设计计算器的 GUI 界面，理解使用 Java中的布局管理器。package lab4;public class MyFrame extends JFrame private JButton btn0=new JButton(0); private JButton btn1=new JButton(1); private JButton btn2=new JButton(2); private JButton btn3=new JButton(3); private JButton btn4=new JButton(4); private JButton btn5=new JButt
10、on(5);private JButton btn6=new JButton(6);private JButton btn7=new JButton(7);private JButton btn8=new JButton(8);private JButton btn9=new JButton(9);private JButton btnpoint=new JButton(.);private JButton btnsqrt=new JButton(? );private JButton btnadd=new JButton(+);private JButton btnsub=new JButt
11、on(-);private JButton btnmul=new JButton(*);private JButton btndiv=new JButton(/);private JButton btnback=new JButton(? ?);private JButton btnsin=new JButton(sin);private JButton btnequ=new JButton(=);private JButton btnclear=new JButton(CE);private JTextArea input=new JTextArea(2,21);private JTextA
12、rea show=new JTextArea(Result:n,2,21);private String result=;private ArrayList signpos=new ArrayList(); public MyFrame(String title)this();setTitle(title);private MyFrame()setLayout(new FlowLayout(FlowLayout.LEADING); setSize(250, 250);setResizable(false); setDefaultCloseOperation(JFrame.EXIT_ON_CLO
13、SE); setLocationRelativeTo(null);/? ?D show.setEditable(false);input.setEditable(false);add(input);add(show);add(btn7);add(btn8);add(btn9);add(btndiv);add(btnsqrt);add(btn4);add(btn5);add(btn6);add(btnmul); add(btnback); add(btn1); add(btn2); add(btn3);add(btnsub); add(btnclear);add(btn0); add(btnpo
14、int); add(btnsin); add(btnadd); add(btnequ);btn0.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+0););btn1.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+1
15、););btn2.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+2););btn3.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+3););btn4.addActionListener(new ActionLis
16、tener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+4););btn5.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+5););btn6.addActionListener(new ActionListener() Overridepublic void actionPerfor
17、med(ActionEvent e) input.setText(input.getText()+6););btn7.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+7););btn8.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.g
18、etText()+8););btn9.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+9););btnpoint.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(input.getText()+.););btnadd.addActionListen
19、er(new ActionListener() Override public void actionPerformed(ActionEvent e) signpos.add(input.getText().length(); input.setText(input.getText()+););btnsub.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) signpos.add(input.getText().length(); input.setText(inp
20、ut.getText()+-););btnmul.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) signpos.add(input.getText().length(); input.setText(input.getText()+*););btndiv.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) signpos.add(inp
21、ut.getText().length(); input.setText(input.getText()+/););btnsin.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) double res; if(!input.getText().isEmpty()/!input.getText().equals() /!input.getText()= error!res=Double.parseDouble(input.getText(); show.setText
22、(sin +input.getText()+ = +Math.sin(res); input.setText();else if(!result.isEmpty()res=Double.parseDouble(result); show.setText(sin +result+ = +Math.sin(res); input.setText(););btnequ.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) String in=input.getText();
23、if(signpos.size()=0) return; double first;String tmp=;if(in.charAt(0)=+|in.charAt(0)=-|in.charAt(0)=*|in.charAt(0)=/)first=Double.parseDouble(result);tmp=result.substring(result.indexOf(=)+1);elsefirst=Double.parseDouble(in.substring(0, signpos.get(0);result=String.valueOf(operator(first,0,in);show.
24、setText(tmp+in+ = +result);input.setText();signpos.clear(););btnsqrt.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) double res;if(!input.getText().isEmpty()/!input.getText().equals() /!input.getText()= error!res=Double.parseDouble(input.getText();show.setTe
25、xt(Sqrt +input.getText()+ = +Math.sqrt(res); input.setText();else if(!result.isEmpty()res=Double.parseDouble(result);show.setText(Sqrt +result+ = +Math.sqrt(res);input.setText(););btnback.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) String in=input.getTex
26、t();if(in.isEmpty() return;input.setText(in.substring(0, in.length()-1);if(in.endsWith(+)|in.endsWith(-)|in.endsWith(*)|in.endsWith(/)signpos.remove(signpos.size()-1););btnclear.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) input.setText(); signpos.clear()
27、;);private double operator(double operA,int i,String str) double operB=i=signpos.size()-1?Double.parseDouble(str.substring(signpos.get(i)+1) :Double.parseDouble(str.substring(signpos.get(i)+1,signpos.get(i+1) );switch(str.charAt(signpos.get(i) case +: operA+=operB;break;case -: operA-=operB; break;case *:operA*=operB;break;case /:operA/=operB; break; if(i=signpos.size()-1)return operA;elsereturn operator(operA,i+1,str);public static void main(String args) ? );MyFrame mf=new MyFrame( ? ? mf.setVisible(true);