3. 常见的错误和异常

3.1 Error

最常见的就是 VirtualMachineError，它有两个经典的子类：StackOverflowError、OutOfMemoryError。

package com.atguigu.exception;

import org.junit.Test;

public class TestStackOverflowError {
    @Test
    public void test01(){
        //StackOverflowError
        recursion();
    }

    public void recursion(){ //递归方法
        recursion(); 
    }
}

package com.atguigu.exception;

import org.junit.Test;

public class TestOutOfMemoryError {
    @Test
    public void test02(){
        //OutOfMemoryError
        //方式一：
        int[] arr = new int[Integer.MAX_VALUE];
    }
    @Test
    public void test03(){
        //OutOfMemoryError
        //方式二：
        StringBuilder s = new StringBuilder();
        while(true){
            s.append("atguigu");
        }
    }
}

3.2 运行时异常

package com.atguigu.exception;

import org.junit.Test;

import java.util.Scanner;

public class TestRuntimeException {
    @Test
    public void test01(){
        //NullPointerException
        int[][] arr = new int[3][];
        System.out.println(arr[0].length);
    }

    @Test
    public void test02(){
        //ClassCastException
        Object obj = 15;
        String str = (String) obj;
    }

    @Test
    public void test03(){
        //ArrayIndexOutOfBoundsException
        int[] arr = new int[5];
        for (int i = 1; i <= 5; i++) {
            System.out.println(arr[i]);
        }
    }

    @Test
    public void test04(){
        //InputMismatchException
        Scanner input = new Scanner(System.in);
        System.out.print("请输入一个整数：");//输入非整数
        int num = input.nextInt();
        input.close();
    }

    @Test
    public void test05(){
        int a = 1;
        int b = 0;
        //ArithmeticException
        System.out.println(a/b);
    }
}

3.3 编译时异常

package com.atguigu.exception;

import org.junit.Test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class TestCheckedException {
    @Test
    public void test06() {
        Thread.sleep(1000);//休眠1秒  InterruptedException
    }

    @Test
    public void test07(){
        Class c = Class.forName("java.lang.String");//ClassNotFoundException
    }

    @Test
    public void test08() {
        Connection conn = DriverManager.getConnection("....");  //SQLException
    }
    @Test
    public void test09()  {
        FileInputStream fis = new FileInputStream("尚硅谷Java秘籍.txt"); //FileNotFoundException
    }
    @Test
    public void test10() {
        File file = new File("尚硅谷Java秘籍.txt");
		FileInputStream fis = new FileInputStream(file);//FileNotFoundException
		int b = fis.read();//IOException
		while(b != -1){
			System.out.print((char)b);
			b = fis.read();//IOException
		}
		
		fis.close();//IOException
    }
}