J2SE之_异常处理

异常的概念

异常的分类

异常的捕获和处理

import java.io.*;

public class TestEx {
    public static void main(String[] args) {

        try {
            new TestEx().f2();
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*
        int[] arr = {1, 2, 3};
        System.out.println(arr[2]);
        try {
            System.out.println(2/0);
        } catch (ArithmeticException e) {
            System.out.println("系统正在维护,请与管理员联系");
            e.printStackTrace();
        }
        */

        //TestEx te = new TestEx();
        //te.m(0);

        /*
        try {
            new TestEx().m(0);
        } catch (ArithmeticException ae) {
            ae.printStackTrace();
            System.out.println("出错了");
        }
        */

        FileInputStream in = null;

    try {
        in = new FileInputStream("myfile.txt");
        int b;
        b = in.read();
        while (b != -1) {
            System.out.print((char) b);
            b = in.read();
        }
    } catch (IOException e) {
      System.out.println(e.getMessage());

    } catch (FileNotFoundException e) {
        e.printStackTrace(); 

    } finally {
        try {
          in.close();
      } catch (IOException e) {
          e.printStackTrace();
      }
    }

    }

    void m(int i) throws ArithmeticException {
        if(i==0)
            throw new ArithmeticException("被除数为0");
    }

    void f() throws FileNotFoundException , IOException {
        FileInputStream in = new FileInputStream("myfile.txt");
    int b;
    b = in.read();
    while (b != -1) {
        System.out.print((char) b);
        b = in.read();
    }
    }

    void f2() throws IOException {
        /*
        try {
            f();
        } catch (FileNotFoundException e) {
            System.out.println(e.getMessage());
        } catch (IOException e) {
            e.printStackTrace();
        }
        */
        f();
    }

}

TestEx.java

使用自定义的异常

声明并抛出异常