java 缺憾:异常的丢失

一.java的异常实现也是又缺陷的,异常作为程序出错的标志决不能被忽略,但它还是可能被轻易地忽略.下了可以看到前一个异常还没处理就抛出下一个异常,没有catch捕获异常,它被finally抛出下一个异常所取代

//: exceptions/LostMessage.java
// How an exception can be lost.
package object;
class VeryImportantException extends Exception {
  public String toString() {
    return "A very important exception!";
  }
}

class HoHumException extends Exception {
  public String toString() {
    return "A trivial exception";
  }
}

public class LostMessage {
  void f() throws VeryImportantException {
    throw new VeryImportantException();
  }
  void dispose() throws HoHumException {
    throw new HoHumException();
  }
  public static void main(String[] args) {
    try {
      LostMessage lm = new LostMessage();
      try {
        lm.f();
      } finally {
        lm.dispose();
      }
    } catch(Exception e) {
      System.out.println(e);
    }
  }
} /* Output:
A trivial exception
*///:~

二.在finally中加入return语句,没有用catch语句捕获异常,下面这种情况编译器会报警:finally块未正常完成

package exceptions;
//: exceptions/ExceptionSilencer.java

public class ExceptionSilencer {
  public static void main(String[] args) {
    try {
      throw new RuntimeException();
    } finally {
      // Using 'return' inside the finally block
      // will silence any thrown exception.
      return;
    }
  }
} ///:~