java方法重写中声明异常的原则
子类声明异常的范围不能超过父类声明的范围：
1. 父类没有声明异常，子类也不能；
2.不可以抛出原有方法抛出异常类的父类或者上层类
3.抛出的异常类型数目不可以比原有方法抛出的还多
例如：
import java.io.FileNotFoundException;
import java.io.IOException;
import java.text.ParseException;
import java.time.format.DateTimeParseException;
import java.util.zip.DataFormatException; import java.io.FileNotFoundException; import java.io.IOException; import java.text.ParseException; import java.time.format.DateTimeParseException; import java.util.zip.DataFormatException;
import java.io.IOException;
import java.text.ParseException;
import java.time.format.DateTimeParseException;
import java.util.zip.DataFormatException; import java.io.FileNotFoundException; import java.io.IOException; import java.text.ParseException; import java.time.format.DateTimeParseException; import java.util.zip.DataFormatException;
public class A {
public void s() throws IOException{ }
} public class A { public void s() throws IOException{ } }
public void s() throws IOException{ }
} public class A { public void s() throws IOException{ } }
class B extends A{
public void s() throws FileNotFoundException{ }
} class B extends A{ public void s() throws FileNotFoundException{ } }
public void s() throws FileNotFoundException{ }
} class B extends A{ public void s() throws FileNotFoundException{ } }
class C extends A{
public void s(){ }
} class C extends A{ public void s(){ } }
public void s(){ }
} class C extends A{ public void s(){ } }
class D extends A{
public void s() throws IOException,FileNotFoundException{ }
} class D extends A{ public void s() throws IOException,FileNotFoundException{ } }
public void s() throws IOException,FileNotFoundException{ }
} class D extends A{ public void s() throws IOException,FileNotFoundException{ } }
class E extends A{
public void s() throws IOException,ArithmeticException,DateTimeParseException{ }
}
class F extends A{
public void s() throws Exception{ }//拋出了父类抛出异常类的父类，错误
} class E extends A{ public void s() throws IOException,ArithmeticException,DateTimeParseException{ } } class F extends A{ public void s() throws Exception{ }//拋出了父类抛出异常类的父类，错误 }
public void s() throws IOException,ArithmeticException,DateTimeParseException{ }
}
class F extends A{
public void s() throws Exception{ }//拋出了父类抛出异常类的父类，错误
} class E extends A{ public void s() throws IOException,ArithmeticException,DateTimeParseException{ } } class F extends A{ public void s() throws Exception{ }//拋出了父类抛出异常类的父类，错误 }
class G extends A{
public void s() throws IOException,DataFormatExceptionException{ } class G extends A{ public void s() throws IOException,DataFormatExceptionException{ }
public void s() throws IOException,DataFormatExceptionException{ } class G extends A{ public void s() throws IOException,DataFormatExceptionException{ }
//错误,因为DataFormatExceptionException的父类也是Exception，所以超出了范围
} //错误,因为DataFormatExceptionException的父类也是Exception，所以超出了范围 }
} //错误,因为DataFormatExceptionException的父类也是Exception，所以超出了范围 }
