我可以在Java中更改循环内的变量名称吗

发布于 2024-10-15 21:30:41 字数 675 浏览 1 评论 0原文

我想在每次迭代时更改变量名称。由于创建的节点数量是动态变化的。

我尝试使用一维数组，但它返回一个空指针。我的代码如下

    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);
    }

我正在使用已经构建的数据结构

    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;
}

java或JSP中是否有其他方法可以在循环内动态更改变量名称。

原文

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.

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故事和酒 2024-10-22 21:30:41

GenericTreeNode<String> root1[] = null;

这一行与这一行等效：

GenericTreeNode<String>[] root1 = null;

因此您创建了一个数组变量并将其初始化为 null

root1[i] =new GenericTreeNode<String>(str);

，但在这里您为数组的索引分配了一个值。

这必须抛出NullPointerException!!。

操作方法如下：

GenericTreeNode<String>[] root1 = new GenericTreeNode<String>[10];

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];

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回梦 2024-10-22 21:30:41

不，您不能更改 Java 中的变量名称。

使用数组时出现 NullPointerException，因为您尝试将值放入数组中，但数组为空。您必须使用正确数量的元素来初始化数组：

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);
}

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);
}

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栩栩如生 2024-10-22 21:30:41

您可能想这样做：

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);
}

不需要“更改变量名称”。

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".

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