异常继承

java异常继承结构图

可以从图中发现， Error, Exception都是继承于Throwable，
关于Error,Exception的异同点可以查看这里写链接内容

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本文描述在继承中有关异常的总结：

1. 基类中方法没有声明抛出异常时， 其子类重写该方法时也不能抛出任何异常

package com.mjlf.myBatis.accessControl.animal;/** * Created by a123 on 16/12/25. */public class ExceptionA extends ExceptionB {    @Override    public void testException() throws Exception{    }    public static void main(String[] args){}}class ExceptionB{    public void testException(){    }}/*Error:(11, 17) java: com.mjlf.myBatis.accessControl.animal.ExceptionA中的testException()无法覆盖com.mjlf.myBatis.accessControl.animal.ExceptionB中的testException()  被覆盖的方法未抛出java.lang.Exception*/

2.基类方法抛出异常，子类要么不抛出异常， 要么抛出异常为基类方法抛出异常或基类方法抛出异常的子异常

package com.mjlf.myBatis.accessControl.animal;/** * Created by a123 on 16/12/25. */public class ExceptionA extends ExceptionB {    @Override    public void testException() throws Exception{    }    public static void main(String[] args){}}class ExceptionB{    public void testException() throws ExceptionC{    }}class ExceptionC extends Exception{}/**Error:(11, 17) java: com.mjlf.myBatis.accessControl.animal.ExceptionA中的testException()无法覆盖com.mjlf.myBatis.accessControl.animal.ExceptionB中的testException()  被覆盖的方法未抛出java.lang.Exception*/

package com.mjlf.myBatis.accessControl.animal;/** * Created by a123 on 16/12/25. */public class ExceptionA extends ExceptionB {    @Override    public void testException() throws ExceptionC{    }    public static void main(String[] args){        System.out.println("yes");    }}class ExceptionB{    public void testException() throws Exception{    }}class ExceptionC extends Exception{}/**yesProcess finished with exit code 0*/

3 . 构造器不遵循上述规则，因为构造器不遵循JAVA的覆盖和重载规则。

class TestA {      public TestA() throws IOException {}      public TestA(int i) {}  }  class TestC extends TestA {      // compiles fine if current constructor doesn't throw anything.      public TestC() { super(0); }  }  class TestB extends TestA {      // compiles fine even if current constructor throws exceptions which don't      // inherit from exceptions that are thrown by the overrided method of the      // base class      // this also means constructors don't conform the inheriting system of JAVA      // class      public TestB() throws Exception {}  }  

4 . 当一个类同时继承另一个类和实现一个接口是， 而这个接口和类中同时用一个相同的方法，但是这个方法抛出了不同的异常时， 这时子类方法要么选择不抛出异常， 要么抛出异常为接口方法和基类方法抛出异常的交集， 否则该方法编译报错

class ExceptionA extends Exception {}class ExceptionB extends Exception {}interface TestA {    void method() throws ExceptionA;}abstract class TestB {    abstract void method() throws ExceptionB;}class TestC extends TestB implements TestA {    //compiles error      public void method() throws ExceptionA {    }}class TestD extends TestB implements TestA {    //compiles error      public void method() throws ExceptionB {    }}class TestE extends TestB implements TestA {    //compiles error      public void method() throws ExceptionA, ExceptionB {    }}class TestF extends TestB implements TestA {    //compiles fine      public void method() {    }}  /**Error:(23, 17) java: com.mjlf.myBatis.accessControl.animal.TestC中的method()无法覆盖com.mjlf.myBatis.accessControl.animal.TestB中的method()  被覆盖的方法未抛出com.mjlf.myBatis.accessControl.animal.ExceptionAError:(29, 17) java: com.mjlf.myBatis.accessControl.animal.TestD中的method()无法实现com.mjlf.myBatis.accessControl.animal.TestA中的method()  被覆盖的方法未抛出com.mjlf.myBatis.accessControl.animal.ExceptionB  Error:(35, 17) java: com.mjlf.myBatis.accessControl.animal.TestE中的method()无法实现com.mjlf.myBatis.accessControl.animal.TestA中的method()  被覆盖的方法未抛出com.mjlf.myBatis.accessControl.animal.ExceptionB*/

package com.mjlf.myBatis.accessControl.animal;//交集使用class ExceptionA extends Exception {    public static void main(String[] args) {    }}class ExceptionB extends Exception {}interface TestA {    void method() throws ExceptionA, ExceptionB;}abstract class TestB {    abstract void method() throws ExceptionB;}class TestC extends TestB implements TestA {    public void method() throws ExceptionB {    }}class TestD extends TestB implements TestA {    public void method() throws ExceptionB {    }}class TestE extends TestB implements TestA {    public void method() throws ExceptionB {    }}class TestF extends TestB implements TestA {    //compiles fine      public void method() {    }}