一、Java异常(一) Java异常简介及其架构

1、自定义异常

public class ExceptionTest {

public static void main(String[] args) {    // TODO Auto-generated method stub    // Integer it=5;    Integer it = null;    try {        System.out.println("aaaaaaa");        if (true) {// 自己定义的异常            throw new RuntimeException("出差类");        }        // int i=it;        // System.out.println("版斑斑驳驳");        // int [] nums= {2,3,4,5};        // System.out.println(nums[6]);    } catch (RuntimeException e) {        System.out.println("wrong" + e.getMessage());        e.printStackTrace();// 把错误信息打印在控制台，这不是处理异常的好方法，不能随便用        // 处理异常，但是里面什么也没有写，这是吃异常，不能这么写    }    /*     * catch(NullPointerException e ) { System.out.println("i不能为null");     * }catch(ArrayIndexOutOfBoundsException e) { System.out.println("超出索引号"); }     * catch(NullPointerException | ArrayIndexOutOfBoundsException e) {     * System.out.println("发生❌");//jdk1.7以后支持这种写法 }     */    System.out.println("cccccc");}

}

2、在main方法里面调用异常

import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;

public class ExceptionTest2 {

public static void main(String[] args) throws FileNotFoundException, ParseException {    // TODO Auto-generated method stub    try {        if(true) {            //throw new RuntimeException();//抛出来RuntimeException,可以不用处理，            //throw new FileNotFoundException();//除了RuntimeException和其子类外，exception其他异常都要处理            throw new IOException();        }    }catch(FileNotFoundException f) {        f.printStackTrace();    }catch(IOException i) {        i.printStackTrace();    }/*  SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");//自己处理异常    Date date;    try {        date = sdf.parse("2015-03-14");        System.out.println(date);        FileInputStream fis=new FileInputStream("w:\\1.txt");    } catch (ParseException e) {        // TODO Auto-generated catch block        e.printStackTrace();        System.out.println("解析日期出错");    } catch (FileNotFoundException e) {        // TODO Auto-generated catch block        e.printStackTrace();        System.out.println("文件未读取");    }*//*  SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");    Date date = sdf.parse("2015-03-14");    System.out.println(date);    FileInputStream fis=new FileInputStream("w:\\1.txt");*/ //在main处抛出异常    try {  //自己处理异常        test();    } catch (FileNotFoundException e) {        // TODO Auto-generated catch block        e.printStackTrace();    } catch (ParseException e) {        // TODO Auto-generated catch block        e.printStackTrace();    }    test();//在main处抛出异常}static void test() throws ParseException, FileNotFoundException {    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");//把异常抛出去，有调用者处理    Date date = sdf.parse("2015-03-14");    System.out.println(date);    FileInputStream fis=new FileInputStream("w:\\1.txt");}

}

3、调用继承的异常

public class ExceptionTest3 {

public static void main(String[] args) {    // 自定义异常        try {            test(1);//调用者处理异常类        } catch (MyException2 e) {            // TODO Auto-generated catch block            e.printStackTrace();            System.out.println("chuwuo"+e.getMessage());        }}static void test(int i) throws MyException2 {    if(i<10) {        //throw new IllegalArgumentException("wrong");//runtimeexception 不用处理        //throw new MyException1("wrong wrong "); MyException1是runtimeexception子类，不用处理        throw new MyException2("wrong wrong ");//MyException2是exception的子类，异常要处理        //抛出去让调用着处理    }}

}

public class MyException1 extends RuntimeException{

public MyException1() {    super();    // TODO Auto-generated constructor stub}public MyException1(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {    super(message, cause, enableSuppression, writableStackTrace);    // TODO Auto-generated constructor stub}public MyException1(String message, Throwable cause) {    super(message, cause);    // TODO Auto-generated constructor stub}public MyException1(String message) {    super(message);    // TODO Auto-generated constructor stub}public MyException1(Throwable cause) {    super(cause);    // TODO Auto-generated constructor stub}

}

public class MyException2 extends Exception {

public MyException2() {    super();    // TODO Auto-generated constructor stub}public MyException2(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {    super(message, cause, enableSuppression, writableStackTrace);    // TODO Auto-generated constructor stub}public MyException2(String message, Throwable cause) {    super(message, cause);    // TODO Auto-generated constructor stub}public MyException2(String message) {    super(message);    // TODO Auto-generated constructor stub}public MyException2(Throwable cause) {    super(cause);    // TODO Auto-generated constructor stub}

}