Thread: Java Class : How do I set up a toString method for arrays?

I'll walk you through a simple example of how to override the toString() method:

Let's say we have class named A, which had an int variable var which was set in the constructor:

public class A {
     int var = 0;
 
     public A(int n) {
          var = n;
     }
}

Now let's say we want to override A's toString() method to print the value of var 5 times. Our new class would look like:

public class A {
     int var = 0;
 
     public A(int n) {
          var = n;
     }
     public String toString() {
          String ret = var+"";
          ret = ret+var;
          ret = ret+var;
          ret = ret+var;
          ret = ret+var;
          return ret;
     }
}

Now, if we create a main that creates an A Object, and prints out an A Object to the console, our main would look like this:

public class someClass {
     public static void main(String[] args) {
          A aObj = new A(5);
          System.out.println(aObj);
     }
}

and our output would look this like:

55555

Now, that is how to override a toString() method. But what about printing out an array? Well, we can call a println on an array. Let's say we had a main which had an int array with the numbers 1 through 5. Then let's print out the array, both by just calling it, and with each int on its own line:

public class someClass {
     public static void main(String[] args) {
          int[] array = new int[]{1,2,3,4,5};
          System.out.println(array);
          for(int i=0;i<array.length;i++)
               System.out.println(array[i]);
     }
}

And our output would be:

[1, 2, 3, 4, 5]
1
2
3
4
5

With all of that information (and your knowledge of looping through an array which I see you have), see if you can figure some of it out. If you have some trouble, feel free to ask.

a3 = a1.concat(a2)

For that to work, concat() needs to return a TestClass object.

Have you coded the class and compiled it? What happened?
Have you tried the code in post#1?

Please post the full text of the compiler's error message.

What you posted is an execution time error, not a compiler error. There is no stack trace for compiler errors.

Can you post the full text of the compiler error message? The error messages I get include the source line and a ^ under where the error is located:

TestSorts.java:138: cannot find symbol
symbol  : variable var
location: class TestSorts
         var = 2;
         ^

Sorry, you need to use the javac compiler to get good compiler error messages. The error messages I get compiling your code have nothing to do with the length attribute.