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Feb 7th, 2007

my program is compiled.but on run that i have message "Exception in thread "main" jav

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my program is compiled.but on run that i have message "Exception in thread "main" java.lang.NullPointer Exception"

1. class Rev
2. {
3. char a[];
4. char i=3;
5. void str()
6. {
7. for(i='A';i<'D';i++)
8. {
9. a[i]='i';
10. }
11. }
12. void show()
13. {
14. for(int i='A';i<'D';i++)
15. {
16. System.out.print(a[i]);
17. }
18. }
19. void reversStr()
20. {
21. for(i='A';i<'D';i++)
22. {
23. System.out.print(a[i]);
24. }
25. }
26. }
27. class Revers
28. {
29. public static void main(String[] args)
30. {
31. Rev a1=new Rev();
32. a1.str();
33. a1.show();
34. a1.reversStr();
35. }
36. }
37. plz run and solve the problem

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ajay_tabbu

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Feb 7th, 2007

Re: my program is compiled.but on run that i have message "Exception in thread "main"

I think you should reconsider your for loop

Java Syntax (Toggle Plain Text)
for(i='A';i<'D';i++)
for(i='A';i<'D';i++)

I never heard that in java you can increase value of character type variable, this is possible but in Perl
Create array of characters and with use of "i" get the character from the array
so if char[] myArray = { 'A', 'B', 'C'}
then if i = 1
you get character B

peter_budo

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Feb 7th, 2007

Re: my program is compiled.but on run that i have message "Exception in thread "main"

Oh my.

For one, I think this is how you meant to represent your code:

java Syntax (Toggle Plain Text)
class Rev {
    char a[];
    char i=3;
 
    void str() {
        for(i='A';i<'D';i++) {
            a[i]='i';
        }
    }
 
    void show() {
        for(int i='A';i<'D';i++) {
            System.out.print(a[i]);
        }
    }
 
    void reversStr() {
        for(i='A';i<'D';i++) {
            System.out.print(a[i]);
        }
    }
 
}
 
class Revers {
 
    public static void main(String[] args) {
        Rev a1=new Rev();
        a1.str();
        a1.show();
        a1.reversStr();
    }
 
}
class Rev {
    char a[];
    char i=3;
    
    void str() {
        for(i='A';i<'D';i++) {
            a[i]='i';
        }
    }
    
    void show() {
        for(int i='A';i<'D';i++) {
            System.out.print(a[i]);
        }
    }
    
    void reversStr() {
        for(i='A';i<'D';i++) {
            System.out.print(a[i]);
        }
    }
    
}

class Revers {
    
    public static void main(String[] args) {
        Rev a1=new Rev();
        a1.str();
        a1.show();
        a1.reversStr();
    }
    
}

And, I get the error because you're trying to access an array element without having defined the size of the array.

Java Syntax (Toggle Plain Text)
void str() {
    for(i='A';i<'D';i++) {
        a[i]='i'; // ERROR OCCURS HERE
    }
}
void str() {
    for(i='A';i<'D';i++) {
        a[i]='i'; // ERROR OCCURS HERE
    }
}

So, define a length for the array at the start of class Rev: char[] a = new char[(some integer)];

You're still going to end up with issues, such as java.lang.ArrayIndexOutOfBoundsException: 65 when you try to access a['A'] and so on, because 'A' as a char is 65 as an integer, and integers are what you want to work with when accessing arrays.

I have no idea what your program's trying to do, but those are some thing to consider.

Cudmore

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Feb 7th, 2007

Re: my program is compiled.but on run that i have message "Exception in thread "main"

thank you very much

ajay_tabbu

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Feb 7th, 2007

Re: my program is compiled.but on run that i have message "Exception in thread "main"

i m very thankfull 4 r u r help

ajay_tabbu

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Mar 1st, 2010

add program

Java Syntax (Toggle Plain Text)
class addition
{
public static void main(String args[])
{
int a=Integer.parseInt(args[0]);
int b=Integer.parseInt(args[1]);
int c=a+b;
System.out.println("sum="+c);
}
}
class addition
{
public static void main(String args[])
{
int a=Integer.parseInt(args[0]);
int b=Integer.parseInt(args[1]);
int c=a+b;
System.out.println("sum="+c);
}
}

Last edited by peter_budo; Mar 1st, 2010 at 6:34 am. Reason: Keep It Organized - For easy readability, always wrap programming code within posts in [code] (code blocks)

2bikash

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Mar 1st, 2010

Re: my program is compiled.but on run that i have message "Exception in thread "main" jav

Your code only works if args.length >= 2 and if the args can be parsed as integers. In short, it is almost useless. As is upping a thread that is 3 years old.

BestJewSinceJC

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