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1.Java 中的异常处理机制
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编译出错，提示“公有类HelloWorld必须在HelloWorld.java文件中定义”
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（IOException及其子类（FileNotFoundException等），都属于检测型异常；运行时异常可以处理，也可以不处理，是可选的；
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所有的异常类是从 java.lang.Exception 类继承的子类）
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运行时报错，提示除数不能为0
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2.捕获异常
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package step2;
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import java.util.Scanner;
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public class Task {
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public static void main(String[] args) {
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Scanner sc = new Scanner(System.in);
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int num1 = sc.nextInt();
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int num2 = sc.nextInt();
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/********* Begin *********/
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try{
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System.out.println(num1/num2);}
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catch(ArithmeticException e){
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System.out.print("除数不能为0");
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}
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/********* End *********/
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}
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}
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3.抛出异常
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package step3;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import java.io.IOException;
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public class Task {
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public static void main(String[] args)throws FileNotFoundException{
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test();
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}
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public static void test()throws FileNotFoundException{
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File file = new File("abc");
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if(!file.exists()){ //判断文件是否存在
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//文件不存在，则 抛出 文件不存在异常
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throw new FileNotFoundException("该文件不存在");
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}else{
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FileInputStream fs = new FileInputStream(file);
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}
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}
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/********* End *********/
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}
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4.自定义异常
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package step4;
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import java.util.Scanner;
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public class Task {
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/********* Begin *********/
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public static void main(String[] args)throws MyException {
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Scanner sc = new Scanner(System.in);
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String username = sc.next();
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//判断用户名
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if(username.length()<3){
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throw new MyException("用户名小于三位Exception");
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}
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else{
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System.out.println("用户名格式正确");
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}
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}
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}
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class MyException extends Exception{
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public MyException(){}
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public MyException(String msg){
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super(msg);
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}
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}
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/********* End *********/
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