更改Java中数组的大小

Question

I am trying to change the size of a String array, but I don't know what else to try and this method isn't working. Here is my code:

import java.util.Scanner;

public class test{
    public static void main(String[] args){
        String[] names;
        names = new String[5];
        for(int i=0; i<10; ++i){
            addToArray(names, i, "blah");
        }
        System.out.println(names.length);
        System.out.println("bye");
    }

    public static void addToArray(String[] names, int i, String name){
        if (i < names.length){
            names[i] = name;
        }
        else {
            String[] temp;
            temp = new String[names.length + 10];
            System.arraycopy(names, 0, temp, 0, names.length);
            addToArray(temp, i, name);
            names = temp;
        }
    }
}

My problem is that when I run it, it prints that the final length of my array is 5, when it should say 15.

Answer 1

The problem is, you can't change the reference of any of your ( Object ) method arguments, so...

names = temp;

Only changes the reference of the names variable within the context of the addToArray method. You should use a return statement instead...

public static String[] addToArray(String[] names, int i, String name){
    if (i < names.length){
        names[i] = name;
    }
    else {
        String[] temp;
        temp = new String[names.length + 10];
        System.arraycopy(names, 0, temp, 0, names.length);
        names = addToArray(temp, i, name);
    }
    return names;
}

Don't forget to maintain the reference once the method returns...

for(int i=0; i<10; ++i){
    names = addToArray(names, i, "blah");
}

Answer 2

Once an array has been created, the size of that array cannot be changed. An array can hold a fixed amount of objects once created.

An ArrayList however is able to change the amount of objects it holds dynamically. A way to initialize a simple ArrayList would be:

ArrayList<String> stringArrayList = new ArrayList<>();

Answer 3

Three points

1. Arrays are special objects in java, they have a simple attribute named length which is final .
2. Also you are creating a new array, not re-sizing the original array.
3. you can't change the reference of any of your method arguments

Answer 4

change the return type as String[] and return names in addToArray() method and assign names= addToArray(String[] names, int i, String name) ; in mainMethod thus you can maintain the keep tracking with reference when size increases