Java try catch finally 异常 分析

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  public static int method_1() {
        int a = 1;
        try {
         System.out.println("try");
            return a;
        } catch (Exception e) {
            System.out.println("11");
        } finally {
       	   System.out.println("finally");
            ++a;
            return a;

        }

    }

答案：

try
finally
2
即没有异常的情况，先执行try，最后执行finally

---

public static int method_2() {
        int a = 1;
        try {
            System.out.println("try");
            int  u=1/0;
            System.out.println("exception");
            return a;
        } catch (Exception e) {
            System.out.println("catch");
        } finally {
            System.out.println("finally");
            ++a;
            return a;
        }

    }

答案：

try
catch
finally
2
有异常，先捕获，最后finally

---

  public static int method_3() {
        int a = 1;
        try {
            System.out.println("try");
            int  u=1/0;
            System.out.println("exception");
            return a;
        } catch (  Exception e) {
            System.out.println("catch");
            return a;
        } finally {
            System.out.println("finally");
            ++a;

        }

    }

答案：

try
catch
finally
1
方法3和方法2主要的区别在于是catch里面返回还是finally里面返回
当其中只要一个返回时，最后执行其中的返回，但是finally一定会执行

---

 public static int method_4() {
        int a = 1;
        try {
            System.out.println("try");
            int  u=1/0;
            System.out.println("exception");
            return a;
        } catch (  Exception e) {
            System.out.println("catch");
            return a;
        } finally {
            System.out.println("finally");
            ++a;
            return a;
        }
    }

答案：

try
catch
finally
2
当catch和finally都有返回的时候，执行finally返回

---

  public static int method_5() {
        int a = 1;
        try {
            System.out.println("try");
            return a;
        } catch (Exception e) {
            System.out.println("catch");

        } finally {
            System.out.println("finally");
            ++a;
            System.out.println("finally" + a);
        }
        return a;
    }

答案：

try
finally
finally2
1
当没有异常的时候，执行finally，但是其中计算不计入结果

---

多个catch

  public static int method_6() {
        int a = 1;
        try {
            System.out.println("try");
            int  u=1/0;
            return a;
        } catch (  ArithmeticException e) {
            System.out.println("ArithmeticException");
            return a+1;
        } catch (Exception e) {
            System.out.println("Exception");
            return a;
        }finally {
            System.out.println("finally");
            ++a;

        }

    }

答案：

try
ArithmeticException
finally
2

---

 public static int method_7() {
        int a = 1;
        try {
            System.out.println("try");
            int  u=1/0;
            return a;
        } catch (  NullPointerException  e) {
            System.out.println("NullPointerException ");
            return a+1;
        } catch (Exception e) {
            System.out.println("Exception");
            return a;
        }finally {
            System.out.println("finally");
            ++a;

        }

    }

答案：

try
Exception
finally
1

总结

1/0是 ArithmeticException 异常，而非空指针

1. 多个异常，谁第一个捕获了最精确的异常，谁输出
2.  第一个catch没有捕获到异常，由第二个接着捕获