I want to change the variable name with each iteration. Since the number of nodes created is dynamically changing.
I tried using one dimensional array but its returning a null pointer. My code is as follow
GenericTreeNode<String> **root1[]** = null;
for(int i=0;i<10;i++)
{
String str="child"+i;
System.out.println(str);
**root1[i]** =new GenericTreeNode<String>(str);
}
I am using already built datastructure
public class GenericTree<T> {
private GenericTreeNode<T> root;
public GenericTree() {
super();
}
public GenericTreeNode<T> getRoot() {
return this.root;
}
public void setRoot(GenericTreeNode<T> root) {
this.root = root;
}
Is there some other way in java or JSP to change the variable name dynamically inside the loop.
GenericTreeNode<String> root1[] = null;
This line is equivalent to this one:
GenericTreeNode<String>[] root1 = null;
so you create an array variable and initialize it to null
root1[i] =new GenericTreeNode<String>(str);
but here you assign a value to the array's index.
This must throw a NullPointerException
!!.
Here's how to do it:
GenericTreeNode<String>[] root1 = new GenericTreeNode<String>[10];
No, you can't change variable names in Java.
You got a NullPointerException when using an array because you tried to put a value in the array, and the array was null. You have to initialize the array, with the right number of elements :
int length = 10;
GenericTreeNode<String>[] root1 = new GenericTreeNode<String>[length];
for (int i = 0; i < length; i++) {
String str = "child" + i;
System.out.println(str);
root1[i] = new GenericTreeNode<String>(str);
}
You probably mean to do this:
GenericTreeNode<String> root1[] = new GenericTreeNode<String>[10];
for(int i=0;i<10;i++)
{
String str="child"+i;
System.out.println(str);
root1[i] = new GenericTreeNode<String>(str);
}
There's no need to "change a variable name".
No, a variable name can't be changed. Try another method like a 2-dimensional array to create another "variable" as you're iterating.
I not able to initiate GenericTree as array. Later I used just vector to solve the problem.
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