上機題目及答案代碼

1、Java上機實踐三實驗題目1假設字符串s1、s2、s3的定義如下：String s1 = “A String”;String s2 = “A String”;String s3 = s1;請寫出下列表達式的值：s1 = s2s1 = s3s1.length()s1.equals(s2)s1.equals(s3)pareTo(s2)pareTo(s3)s1.concat(s3)s1.indexOf(t)s3.lastIndexOf(t)實驗目的（1） 熟悉字符串類String。（2） 學習創(chuàng)建類String的對象。（3） 學習使用類String執(zhí)行字符串操作。實驗步驟（1） 按題目的要求創(chuàng)建St

2、ring對象s1、s2，并聲明對象引用s3指向s1；（2） 調用String類的相關方法，執(zhí)行指定操作并輸出結果。package lab1;public class Showstr public static void main(String args)String s1 ="A String"String s2 ="A String"String s3 = s1;System.out.println(s1 = s2);System.out.println(s1 = s3);System.out.println(s1.length();System.ou

3、t.println(s1.equals(s2);System.out.println(s1.equals(s3);System.out.println(pareTo(s2);System.out.println(pareTo(s3);System.out.println(s1.concat(s3);System.out.println(s1.indexOf('t');System.out.println(s3.lastIndexOf('t'); 實驗2  Java異常處理 一、實驗目的 1） 掌握Java異常的概

4、念及工作機制 2） 掌握異常的分類 3） 掌握拋出異常語句的使用(throw) 4） 掌握拋出捕獲處理異常語句的使用(trycatchfinally) 5） 掌握上拋異常語句的使用(throws) 6） 掌握創(chuàng)建自定義異常 二、實驗環(huán)境 JDK1.6+Eclpise3.2 三、實驗內容 1、編寫一個應用程序，要求從鍵盤輸入一個double型的圓的半徑，計算并輸出其面積。測試當輸入的數(shù)據(jù)不是double型數(shù)據(jù)（如字符串“abc”）會產(chǎn)生什么結果，怎樣處理。&

5、#160;package lab2;import java.util.InputMismatchException;import java.util.Scanner;public class Err_1 public static void main(String args)Scanner reader=new Scanner(System.in);double r;tryr=reader.nextDouble();System.out.println(3.14*r*r);/System.out.println(3.14*r*r);catch(InputMismatchException e)

6、System.out.println("數(shù)據(jù)類型錯誤"+e.toString();2、計算兩個正數(shù)之和，當任意一個數(shù)超出范圍時，拋出自己定義的異常（NumberRangeException）。package lab2;import java.util.Scanner;import piler.sym;class NumberRangeException extends ExceptionNumberRangeException(String msg)super(msg);public class Err_2 public static void main(String ar

7、gs)Scanner 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; System.out.println(a+b);catch(NumberRangeException e)System.out.println(e.toString();實驗3 輸入和

8、輸出 1實驗目的 了解流式輸入輸出的基本原理；掌握類File、FileInputStream、FileOutputStream的使用方法。 2實驗內容 （1）編程：檢查C:WINDOWSsetuplog.txt文件是否存在，若在則顯示該文件的名稱和內容。 package lab3;import java.io.File;import java.io.IOException;import java.util.Scanner;public class Inoutprivate static Scanner in;public static void main(String args)throws

9、IOExceptiontryFile f1=new File("C:WINDOWSsetuplog.txt");System.out.println("Do this file exist?t"+f1.exists();System.out.println(f1.getName();in = new Scanner(new File("C:WINDOWSsetuplog.txt"); while (in.hasNextLine() String str = in.nextLine(); System.out.println(str);

10、 catch(IOException e)System.out.println(e.getMessage();（2）編程：輸入5個學生的信息（包含學號、姓名、3科成績），統(tǒng)計各學生的總分，然后將學生信息和統(tǒng)計結果存入二進制數(shù)據(jù)文件STUDENT.DAT中。3實驗要求 編程時，應考慮異常處理。package lab3;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectOutputStream;import java.io.RandomAccessFile;import java.util

11、.Scanner;import javafx.beans.value.WritableObjectValue;class StudentString snum;String name;int a,b,c,sum;public void Info()Scanner reader=new Scanner(System.in);System.out.println("Please enter the name:");name=reader.next();System.out.println("Please enter the student number:")

12、;snum=reader.next();System.out.println("Please enter three courses'sorce:");a=reader.nextInt();b=reader.nextInt();c=reader.nextInt();sum=a+b+c;reader.close();public class Inout_2public static void main(String args)throws IOExceptiontryFileOutputStream raf=new FileOutputStream("dar

13、i.txt",true);ObjectOutputStream out=new ObjectOutputStream(raf);Student stu=new Student5;for(int i=0;i<5;i+)stui=new Student();(stui).Info();out.writeObject(stui);out.close();catch(IOException ioe)System.out.println(ioe);catch(Exception e)System.out.println(e);實驗題目4設計計算器的GUI界面，理解使用Java中的布局管理

14、器。package lab4; import java.awt.FlowLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.WindowEvent;import java.awt.event.WindowListener;import java.util.ArrayList; import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JTextArea; publ

15、ic 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=ne

16、w JButton("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=n

17、ew JButton("¡Ì"); private JButton btnadd=new JButton("+"); private JButton btnsub=new JButton("-"); private JButton btnmul=new JButton("*"); private JButton btndiv=new JButton("/"); private JButton btnback=new JButton("¡û&quo

18、t;); 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 JTextArea show=new JTextArea("Result:n",2,21); private String result="

19、;" private ArrayList<Integer> signpos=new ArrayList<Integer>(); public MyFrame(String title) this(); setTitle(title); private MyFrame() setLayout(new FlowLayout(FlowLayout.LEADING); setSize(250, 250); setResizable(false); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setLocationRe

20、lativeTo(null);/¾ÓÖÐ 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(

21、btn0); add(btnpoint); add(btnsin); add(btnadd); add(btnequ); btn0.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText()+"0"); ); btn1.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e

22、) input.setText(input.getText()+"1"); ); btn2.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText()+"2"); ); btn3.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.se

23、tText(input.getText()+"3"); ); btn4.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText()+"4"); ); btn5.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(inpu

24、t.getText()+"5"); ); btn6.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText()+"6"); ); btn7.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText(

25、)+"7"); ); btn8.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText()+"8"); ); btn9.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText()+"9&

26、quot;); ); btnpoint.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) input.setText(input.getText()+"."); ); btnadd.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) signpos.add(input.getText().length(); inpu

27、t.setText(input.getText()+"+"); ); btnsub.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) signpos.add(input.getText().length(); input.setText(input.getText()+"-"); ); btnmul.addActionListener(new ActionListener() Override public void act

28、ionPerformed(ActionEvent e) signpos.add(input.getText().length(); input.setText(input.getText()+"*"); ); btndiv.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) signpos.add(input.getText().length(); input.setText(input.getText()+"/"); );

29、btnsin.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e) double res; if(!input.getText().isEmpty()/!input.getText().equals("") /!input.getText()="" error! res=Double.parseDouble(input.getText(); show.setText("sin "+input.getText(

30、)+" = "+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() Override public void actionPerform

31、ed(ActionEvent e) String in=input.getText(); 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

32、); else first=Double.parseDouble(in.substring(0, signpos.get(0); result=String.valueOf(operator(first,0,in); show.setText(tmp+in+" = "+result); input.setText(""); signpos.clear(); ); btnsqrt.addActionListener(new ActionListener() Override public void actionPerformed(ActionEvent e

33、) double res; if(!input.getText().isEmpty()/!input.getText().equals("") /!input.getText()="" error! res=Double.parseDouble(input.getText(); show.setText("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(