JAVA异常总结 ------ 继承

以下是对JAVA异常的继承机制的一些总结。

1. RuntimeException与Exception, Error不同点： 当方法体中抛出非RuntimeException（及其子类）时，方法名必须声明抛出的异常；但是当方法体中抛出RuntimeException（包括RuntimeException子类）时，方法名不必声明该可能被抛出的异常，即使声明了，JAVA程序在某个调用的地方，也不需要try-catch从句来处理异常。

 

class TestA{//compiles fine.we don't need to claim the RuntimeException to be thrown herevoid method(){throw new RuntimeException();}}class TestB{void method() throws RuntimeException{throw new RuntimeException();}void invokeMethod(){//compiles fine. we don't need the try-catch clause heremethod();}}class TestC{//compiles error.we need to claim the Exception to be thrown on the method name void method(){throw new Exception();}}class TestD{//compiles fine.void method() throws Exception{throw new Exception();}}

 

以下所有的相关异常的特性都不包括RuntimeException及其子类。

2. 假如一个方法在父类中没有声明抛出异常，那么，子类覆盖该方法的时候，不能声明异常。

class TestA{void method(){}}class TestB extends TestA{//complies error if the method overrided pertaining to the base class doesn't declare throwing exceptionsvoid method() throws Exception{throw new Exception();}}

 

3. 假如一个方法在父类中声明了抛出异常，子类覆盖该方法的时候，要么不声明抛出异常，要么声明被抛出的异常继承自它所覆盖的父类中的方法抛出的异常。

class TestA{       void method() throws IOException{}   }   class TestB extends TestA{       //compiles fine if current method does not throw any exceptions       void method(){}   }   class TestC extends TestA{       //compiles fine because InterruptedIOException is inherited from IOException which is thrown by the overrided method of the base class       void method() throws InterruptedIOException{}   }   class TestD extends TestA{       //compiles error because Exception thrown by current method is not inherited from IOException which is thrown by the overrided method of the base class       void method() throws Exception{}   }  

 

4. 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// classpublic TestB() throws Exception {}}

5. 当一个类继承某个类，以及实现若干个接口，而被继承的类与被实现的接口拥有共同的方法，并且该方法被覆盖时，它所声明抛出的异常必须与它父类以及接口一致。

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 errorpublic void method() throws ExceptionA{}}class TestD extends TestB implements TestA{//compiles errorpublic void method() throws ExceptionB{}}class TestE extends TestB implements TestA{//compiles errorpublic void method() throws ExceptionA,ExceptionB{}}class TestF extends TestB implements TestA{//compiles finepublic void method(){}}