1. java所有异常分类

Exception
│
├─ RuntimeException
│  │
│  ├─ NullPointerException
│  │
│  ├─ IndexOutOfBoundsException
│  │
│  ├─ SecurityException
│  │
│  └─ IllegalArgumentException
│     │
│     └─ NumberFormatException
│
├─ IOException
│  │
│  ├─ UnsupportedCharsetException
│  │
│  ├─ FileNotFoundException
│  │
│  └─ SocketException
│
├─ ParseException
│
├─ GeneralSecurityException
│
├─ SQLException
│
└─ TimeoutException

2. 捕获异常

public static void main(String[] args) {
    try {
        process1();
        process2();
        process3();
    } catch (IOException e) {
        System.out.println(e);
    } catch (NumberFormatException e) {
        System.out.println(e);
    }
}

2.1. 捕获异常catch 的顺序

public static void main(String[] args) {
    try {
        process1();
        process2();
        process3();
    } catch (IOException e) {
        System.out.println("IO error");
    } catch (UnsupportedEncodingException e) { 
        System.out.println("Bad encoding");
    }
}

改正：

public static void main(String[] args) {
    try {
        process1();
        process2();
        process3();
    } catch (UnsupportedEncodingException e) {
        System.out.println("Bad encoding");
    } catch (IOException e) {
        System.out.println("IO error");
    }
}

2.2. finally语句

public static void main(String[] args) {
    try {
        process1();
        process2();
        process3();
    } catch (UnsupportedEncodingException e) {
        System.out.println("Bad encoding");
    } catch (IOException e) {
        System.out.println("IO error");
    } finally {
        System.out.println("END");
    }
}

3. 抛出异常

NumberFormatException ne = new NumberFormatException();
throw ne;

// 简洁写法
throw new NumberFormatException();

class GoogleAbnor {
    public void googleAbnor(String s) throws NumberFormatException {
        // NumberFormatException ne = new NumberFormatException();
        // throw ne;
        if (s == null) {
            throw new NumberFormatException();
        } else {
            System.out.println("String fine");
        }
    }
}


class Abnor {
    public void abnor() {
        GoogleAbnor ga = new GoogleAbnor();
        ga.googleAbnor(null);
    }
}


public class AbnormalLearn  {
    public static void main(String[] args) {
        GoogleAbnor gab = new GoogleAbnor();

        try {
            gab.googleAbnor("Hello");
        } catch (Exception e) {
            System.out.println("Catch NumberFormatException");
            e.printStackTrace();
        }

        Abnor ab = new Abnor();
        ab.abnor();
    }
}

------------------------------------------------------------------------------------------------
执行结果：可以看到已经抛出了我们的异常

String fine
Exception in thread "main" java.lang.NumberFormatException
	at com.zhbi.source.GoogleAbnor.googleAbnor(AbnormalLearn.java:10)
	at com.zhbi.source.Abnor.abnor(AbnormalLearn.java:21)
	at com.zhbi.source.AbnormalLearn.main(AbnormalLearn.java:38)
Java Result: 1

4. 异常的传递