Checked Exceptions - What did I wrong?

[Thomas Markl]

Exceptions – What did I wrong?

class Readtest1 {
  public static void main(String args []) {
    while (true) {
      int ch = System.in.read();
      if (ch == 'x')
        break;
    }
  System.out.println("w was read");
  }
}
C:\Java\EigeneJavaProgramme>javac Readtest1.java 
Readtest1.java:6: unreported exception java.io.IOException; must be caught or declared to be thrown
      int ch = System.in.read();
                        ^

I corrected the program by catching the IOException but this error emerges:

class Readtest1 {
  public static void main(String args []) {
    while (true) {
      try {
        int ch = System.in.read();
        if (ch == 'x')
          break;
      } catch (IOException e) {
        System.err.println("Exception caught: " + e.getMessage());
      }
    }
  System.out.println("w was read");
  }
}
 
C:\Java\EigeneJavaProgramme>javac Readtest1.java 
Readtest1.java:10: cannot resolve symbol
symbol  : class IOException  
location: class Readtest1
     } catch (IOException e) {
              ^
1 error

Why this error? What can I do?
[ edited to preserve formatting using the [code] and [/code] UBB tags -ds ]
[ July 26, 2002: Message edited by: Dirk Schreckmann ]

[Anthony Villanueva]

IOException belongs to another package. You are using the java.lang package which is always loaded by default. Use
import java.io.*;
as your first line of code.

[Frank Carver]

Or, even better, explicitly include just the class(es) you are using. In this case:
import java.io.IOException;
This helps people reading the source code to understand what classes it uses from which packages, and helps to prevent confusion when two imported packages have the same class name (e.g. java.awt.List and java.util.List).

[Thomas Markl]

When I run this program with JDK1.3 it works. When I run it with JDK1.4 it produces errors:

import java.io.IOException;
 
class Readtest1a {
  public static void main(String args []) {
    while (true) {
      try {
        int ch = System.in.read();
        if (ch == 'x')
          break;
      } catch (IOException e) {
        System.err.println("Exception caught: " + e.getMessage());
      }
    }
    System.out.println("w was read");
  }
}

When I run this programm with jdk1.3 compiler this programm works.
When I run this programm with jdk1.4 compiler this programm throws this errors:

C:\Java\EigeneJavaProgramme>java Readtest1 
java.io.IOException: Die Zugriffsnummer ist nicht definiert
    at java.io.FileInputStream.readBytes(Native Method)
    at java.io.FileInputStream.read(FileInputStream.java:192)
    at java.io.BufferedInputStream.fill(BufferedInputStream.java:183)
    at java.io.BufferedInputStream.read(BufferedInputStream.java:201)
    at Readtest1.main(Readtest1.java:6)
Exception in thread "main"

[ edited to preserve formatting using the [code] and [/code] UBB tags -ds ]
[ July 26, 2002: Message edited by: Dirk Schreckmann ]

[Dirk Schreckmann]

Your code works fine on my computer running JDK and JRE 1.4.
I do notice that your code prints a specific message ("Exception caught: ") when an IOException is thrown and caught, and that this specific message is not being printed in your error message. Are you certain that you are running the same program?
"Die Zugriffsnummer ist nicht definiert" means "The access number is not defined" - I'm not sure what english version of this error message Java would produce.

[Jim Yingst]

I'm guessing it has nothing to do with this particular Java program, but with how the 1.4 JDK is installed or configured. Try compiling and running a simple "Hello World" in 1.4 to see if everything's OK.

[Frank Carver]

I can't help noticing that your source code example is class Readtest1a, but the error message seems to arise from class Readtest1.
Are you really sure you are recompiling and running the class you think you are?

[Thomas Markl]

Hello,
I tried to start Readtest1a from the DOS-Prompt and it worked.
Then I tried to start it from my texteditor with command: "DOS command to window" and I get this error messages.
What can I do?
Thomas.