实验4 Java异常处理

实验4Java异常处理一、实验目的1、理解异常的基本概念。2、理解throws、try,catch语句的语法格式。3、理解自定义异常类的定义和使用方法。4、掌握Java的异常处理机制、方法与应用。二、实验任务：1、编写一程序实现成绩输入并校验学生成绩，当用户输入-1时表示输入结束。根据正确输入的成绩平均成绩。成绩用实数表示，如果用户输入一个不正确的成绩，如-80、大于100或字符等，程序应该抛出异常，并捕获异常。请使用try和catch语句实现对输入、计算过程中出现的异常进行处理。2、声明一个异常类，即当除数为零时抛出的异常类DivideByZeroException，并在下列代码需要的地方进行异常抛出和异常捕获，以便用户输入出现错误时，程序具有容错功能。本题异常包括除数为零，以及输入数据格式错误，如数据中包含字母。//DivideByZeroTest.java//Asimpleexceptionhandlingexample.//Checkingforadivide-by-zero-error.importjava.text.DecimalFormat;importjavax.swing.*;importjava.awt.*;importjava.awt.event.*;publicclassDivideByZeroTestextendsJFrameimplementsActionListener{privateJTextFieldinput1,input2,output;privateintnumber1,number2;privatedoubleresult;//InitializationpublicDivideByZeroTest(){super("DemonstratingExceptions");Containerc=getContentPane();c.setLayout(newGridLayout(3,2));c.add(newJLabel("Enternumerator",SwingConstants.RIGHT));input1=newJTextField(10);c.add(input1);c.add(newJLabel("EnterdenominatorandpressEnter",SwingConstants.RIGHT));input2=newJTextField(10);c.add(input2);input2.addActionListener(this);c.add(newJLabel("RESULT",SwingConstants.RIGHT));output=newJTextField();c.add(output);setSize(425,100);show();}//ProcessGUIevents//ThrowinganexceptionwhendataformatiswrongorattemptedtodividebyzeropublicvoidactionPerformed(ActionEvente){DecimalFormatprecision3=newDecimalFormat("0.000");output.setText("");number1=Integer.parseInt(input1.getText());number2=Integer.parseInt(input2.getText());result=quotient(number1,number2);output.setText(precision3.format(result));}//Definitionofmethodquotient.Usedtodemonstrate//throwinganexceptionwhenadivide-by-zeroerror//isencountered.publicdoublequotient(intnumerator,intdenominator){return(double)numerator/denominator;}publicstaticvoidmain(Stringargs[]){DivideByZeroTestapp=newDivideByZeroTest();app.addWindowListener(newWindowAdapter(){publicvoidwindowClosing(WindowEvente){e.getWindow().dispose();System.exit(0);}});}}package

zhidao;import

java.awt.event.ActionEvent;import

java.awt.event.ActionListener;import

javax.swing.BorderFactory;import

javax.swing.JFrame;import

javax.swing.JLabel;import

javax.swing.JTextField;import

javax.swing.JTextArea;import

javax.swing.JButton;import

javax.swing.JScrollPane;import

javax.swing.border.BevelBorder;import

javax.swing.JPanel;public

class

StudentScore

extends

JFrame

implements

ActionListener{

private

JTextField

stuId;

private

JTextField

stuScore;

private

JTextArea

allStudent;

private

JButton

button;

private

final

JPanel

panel

=

new

JPanel();

public

StudentScore()

{

setBounds(200,

100,

244,

630);

getContentPane().setLayout(null);

panel.setBounds(0,

0,

228,

592);

getContentPane().add(panel);

panel.setLayout(null);

JLabel

lblNewLabel

=

new

JLabel("\u8F93\u5165\u5B66\u751F\u6210\u7EE9");

lblNewLabel.setBounds(20,

33,

85,

15);

panel.add(lblNewLabel);

JLabel

label

=

new

JLabel("\u8F93\u5165\u5B66\u751F\u7F16\u53F7");

label.setBounds(20,

8,

85,

15);

panel.add(label);

stuId

=

new

JTextField();

stuId.setBounds(113,

5,

105,

21);

panel.add(stuId);

stuId.setColumns(10);

stuScore

=

new

JTextField();

stuScore.setBounds(113,

33,

105,

21);

panel.add(stuScore);

stuScore.setColumns(10);

button

=

new

JButton("\u5F55\u5165");

button.setBounds(84,

64,

80,

23);

panel.add(button);

allStudent

=

new

JTextArea();

JScrollPane

scrollPane

=

new

JScrollPane(allStudent);

scrollPane.setBounds(20,

97,

198,

485);

panel.add(scrollPane);

button.addActionListener(this);

}

@Override

public

void

actionPerformed(ActionEvent

arg0)

{

//监听,try

catch在这里

String

id

=

stuId.getText();

String

score

=

stuScore.getText();

try{

Double

sco

=

Double.valueOf(score);

if(sco

==

-1){

allStudent.append("录入结束");

button.setEnabled(false);

return;

}

if(sco<0

||

sco>100){

throw

new

Exception();

}

allStudent.append("编号："+id+"，成绩："+score);

allStudent.append("\n");

}catch(Exception

e){

allStudent.append("编号为"+id+"的学生成绩输入异常");

allStudent.append("\n");

}

}

public

static

void

main(String[]

args)

{

new

StudentScore().setVisible(true);

}}/DivideByZeroTest.java//Asimpleexceptionhandlingexample.//Checkingforadivide-by-zero-error.importjava.text.DecimalFormat;importjavax.swing.*;importjava.awt.*;importjava.awt.event.*;publicclassDivideByZeroTestextendsJFrameimplementsActionListener{privateJTextFieldinput1,input2,output;privateintnumber1,number2;privatedoubleresult;//InitializationpublicDivideByZeroTest(){super("DemonstratingExceptions");Containerc=getContentPane();c.setLayout(newGridLayout(3,2));c.add(newJLabel("Enternumerator",SwingConstants.RIGHT));input1=newJTextField(10);c.add(input1);c.add(newJLabel("EnterdenominatorandpressEnter",SwingConstants.RIGHT));input2=newJTextField(10);c.add(input2);input2.addActionListener(this);c.add(newJLabel("RESULT",SwingConstants.RIGHT));output=newJTextField();c.add(output);setSize(425,100);show();}//ProcessGUIevents//ThrowinganexceptionwhendataformatiswrongorattemptedtodividebyzeropublicvoidactionPerformed(ActionEvente){DecimalFormatprecision3=newDecimalFormat("0.000");output.setText("");number1=Integer.parseInt(input1.getText());number2=Integer.parseInt(input2.getText());result=quotient(