26.异常

1.异常概述

 2.JVM处理异常的默认方案

 3.异常处理

 3.1  try ...catch...

 4.Throwable的成员方法

 

    public static void main(String[] args) {
        int[] arr = {1, 2, 3};
        System.out.println("开始");
        try {
            run(arr);
        } catch (ArrayIndexOutOfBoundsException throwable) {
            throwable.printStackTrace();
            /**
             * java.lang.ArrayIndexOutOfBoundsException: 3
             *     at throwable.TryCatch.run(TryCatch.java:18)
             *     at throwable.TryCatch.main(TryCatch.java:11)
             */
        }
        System.out.println("结束");
    }

    public static void run(int[] arr) {
        System.out.println(arr[3]);
    }

5.编译时异常和运行时异常

 5.Throws处理异常

 6.自定义异常

  举例

public class ScoreException extends Exception {
    public ScoreException() {
    }

    public ScoreException(String message) {
        super(message);
    }
}

public class CheckScore {

    public void checkScore(int score) throws ScoreException {//由于ScoreException继承自Exception,所以是编译时异常,异常需要进行处理(这里进行抛出处理,由调用者处理

        if (score < 0 || score > 100) {//分数不在正常范围之内,抛出异常
            throw new ScoreException("分数异常,分数应该在0-100之间");
        } else {
            System.out.println("分数正常");
        }
    }
}

    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入分数:");
        int i = scanner.nextInt();
        CheckScore checkScore=new CheckScore();
        try {
            checkScore.checkScore(i);
        } catch (ScoreException e) {
            e.printStackTrace();
        }
    }

 Throws和Throw区别

 补充理解throws和try...catch

throws仅仅是把异常向上抛出,交由调用它的地方去处理,其实并没有实质性的进行处理;

try...catch会处理异常,不影响程序继续向下执行