Java FileInputStream和FileOutputStream错误

Question

I just made my first I/O based stuff in Java. I want to check if the content written to a file is properly saved in, or not. For which i wrote the following code..

    import java.io.*;

    public class check implements Serializable {
        //Make two variables and methods to initialise them
        private int height;
        private int width;
        public void setWidth(int w){
            width = w;
        }
        public void setHeight(int h){
            height = h;
        }
        public static void main(String[] args) {

        check obj = new check();
        obj.setHeight(20);
        obj.setWidth(30);

    try{
        FileOutputStream fs = new FileOutputStream("foo.txt");
        ObjectOutputStream os = new ObjectOutputStream(fs);
        os.writeObject(obj);
        os.close();
    }
    catch(IOException ex){
    }
    //We set them to null so we can't access the objects on heap.
      obj = null;  

    //Now we read them back from file   
    try{
        ObjectInputStream is = new ObjectInputStream(new FileInputStream("foo.txt")); 
        check stored = (check) is.readObject();

    //Check to see if it worked.
     System.out.println("Variable, stored contains.." + stored.getType());
    }
    catch(IOException ex){
        }

    }
 }

But it produces the following error.

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - unreported exception java.lang.ClassNotFoundException; must be caught or declared to be thrown
    at check.Check.main(Check.java:33)

Anyone got any idea to solve the issue?

Answer 1

Take a look at http://docs.oracle.com/javase/7/docs/api/java/io/ObjectInputStream.html#readObject() . The method lists a couple of exceptions. For every exception listed that is not a sub-class of RuntimeException you need to either catch the exception or declare that the method can throw that exception. You have only done this for IOException . You also need to do this for the other exceptions listed in the documentation. This needs to be done for all methods that throw non-runtime exceptions.

Answer 2

Your IDE is letting you run some code even though you are missing some classes or despite having compilation errors. Fix the compilation errors before you run them.

Answer 3

Your code is uncompilable at the moment. Line 36 fails.

System.out.println("Variable, stored contains.." + stored.getType());

This is because the class check does not contain a method getType() . Maybe You meant something along the lines of getClass().getName() ?

Fix this error and try again. Your own error message does not make sense to me - is it generated by an IDE?

PS. Have a look at Java coding conventions regarding the naming of classes, variables and such. :)