异常处理的动手动脑

一，抛异常的类型

抛异常：1,Error错误，系统错误 2,Exception错误
Exception类又包括：RuntimeException非检查异常和检查异常。
Error例子: 1.AssertionError程序运行期间判断某个条件是否满足
,不满足时，抛出AssertionError。

2.OOM Error系统内存不足。

二，小探索

int i=1, j=0, k;
k=i/j;

javac生成idiv字节码指令
double d1=100,d2=0,result;
    result=d1/d2;
System.out.println("浮点数除以零：" + data);

浮点数除以0：Infinity
javac生成ddiv字节码指令，JVM在具体实现这两个指令时，采用了不同的处理策略，导致两段代码运行时得到不同的结果。

三，try catch的嵌套

public class CatchWho {
    public static void main(String[] args) {
        try {
                try {
                    throw new ArrayIndexOutOfBoundsException();
                }
                catch(ArrayIndexOutOfBoundsException e) {
                       System.out.println(  "ArrayIndexOutOfBoundsException" +  "/内层try-catch");
                }

            throw new ArithmeticException();
        }
        catch(ArithmeticException e) {
            System.out.println("发生ArithmeticException");
        }
        catch(ArrayIndexOutOfBoundsException e) {
           System.out.println(  "ArrayIndexOutOfBoundsException" + "/外层try-catch");
        }
    }
}

ArrayIndexOutOfBoundsException/内层try-catch
发生ArithmeticException

上述是结果

public class CatchWho2 {
    public static void main(String[] args) {
        try {
                try {
                    throw new ArrayIndexOutOfBoundsException();
                }
                catch(ArithmeticException e) {
                    System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch");
                }
            throw new ArithmeticException();
        }
        catch(ArithmeticException e) {
            System.out.println("发生ArithmeticException");
        }
        catch(ArrayIndexOutOfBoundsException e) {
            System.out.println( "ArrayIndexOutOfBoundsException" + "/外层try-catch");
        }
    }
}

ArrayIndexOutOfBoundsException/外层try-catch

看下面这段代码，

public class EmbededFinally {

    public static void main(String args[]) {

        int result;

        try {

            System.out.println("in Level 1");

             try {

                System.out.println("in Level 2");
                    //result=100/0;  //Level 2

                 try {

                     System.out.println("in Level 3");

                     result=100/0;  //Level 3

                } 

                catch (Exception e) {

                    System.out.println("Level 3:" + e.getClass().toString());

                }

                finally {

                    System.out.println("In Level 3 finally");

                }

                // result=100/0;  //Level 2

                }

            catch (Exception e) {

                 System.out.println("Level 2:" + e.getClass().toString());

             }
             finally {

                System.out.println("In Level 2 finally");

             }

            // result = 100 / 0;  //level 1

        } 

        catch (Exception e) {

            System.out.println("Level 1:" + e.getClass().toString());

        }

        finally {

            System.out.println("In Level 1 finally");

        }

    }

}

运行结果为

in Level 1
in Level 2
in Level 3
Level 3:class java.lang.ArithmeticException
In Level 3 finally
In Level 2 finally
In Level 1 finally

当有多层嵌套的finally时，异常在不同的层次抛出    ，在不同的位置抛出，会导致不同的finally语句块执行顺序。

四，自定义异常

Class MyException extends Exception
    { …    }
Class MyClass {
        void someMethod() {
            if (条件) throw new MyException();
        }
    }

原文地址：https://www.cnblogs.com/xcl666/p/9938913.html