java 把被检查的异常转换为不检查的异常

Posted 2021-02-05 飞龙dragon

一.当我们不知道该怎么处理这个异常,但是也不想把它"吞"了,或者打印一些无用的信息,可以使用异常链的思路解决.可以直接报"被检查的异常"包装进RuntimeException里面,就像这样:

try{
   //... to do something useful
} catch(IDontKnowWhatToDoWithThisCheckedException e){
 throw new RuntimeException(e);
}

  这种技巧给了你一种选择,你可以不写try-catch子句或异常说明,直接忽略异常,让它自己沿着调用栈往上冒泡.同时还可以用getCause()捕获并处理特定异常,就像这样

package exceptions;
//: exceptions/TurnOffChecking.java
// "Turning off" Checked exceptions.
import java.io.*;
import static net.mindview.util.Print.*;

class WrapCheckedException {
  void throwRuntimeException(int type) {
    try {
      switch(type) {
        case 0: throw new FileNotFoundException();
        case 1: throw new IOException();
        case 2: throw new RuntimeException("Where am I?");
        default: return;
      }
    } catch(Exception e) { // Adapt to unchecked:
      throw new RuntimeException(e);
    }
  }
}

class SomeOtherException extends Exception {}

public class TurnOffChecking {
  public static void main(String[] args) {
    WrapCheckedException wce = new WrapCheckedException();
    // You can call throwRuntimeException() without a try
    // block, and let RuntimeExceptions leave the method:
    wce.throwRuntimeException(3);
    // Or you can choose to catch exceptions:
    for(int i = 0; i < 4; i++)
      try {
        if(i < 3)
          wce.throwRuntimeException(i);
        else
          throw new SomeOtherException();
      } catch(SomeOtherException e) {
          print("SomeOtherException: " + e);
      } catch(RuntimeException re) {
        try {
          throw re.getCause();
        } catch(FileNotFoundException e) {
          print("FileNotFoundException: " + e);
        } catch(IOException e) {
          print("IOException: " + e);
        } catch(Throwable e) {
          print("Throwable: " + e);
        }
      }
  }
} /* Output:
FileNotFoundException: java.io.FileNotFoundException
IOException: java.io.IOException
Throwable: java.lang.RuntimeException: Where am I?
SomeOtherException: SomeOtherException
*///:~