如果我的数组大小在Java中已满，如何动态创建数组的新实例

Question

I am working on a java program. where I have taken an input string and I am putting each char from a string in a 4*4 matrix. If the input string length is small than 16 ie 4*4 matrix, then I am adding padding '#' char.

But Now, suppose the input string length is more than 16 then I want to create a new array and put remaining chars into it. I can't use a vector, set, map. So How can I code now?

here is some code. key=4.

 char[][] giveMeNewArray() {
    char[][] matrix = new char[key][key];
    return matrix;
 }

 void putCharIntoMatrix() {
    int counter = 0;
    char[][] myArray = giveMeNewArray();
    System.out.println("myArray: " + myArray);

    for (int i = 0; i < key; i++) {
        for (int j = 0; j < key; j++) {
            if (counter >= inputString.length()) {
                myArray[i][j] = '#';
            } else {
                myArray[i][j] = inputString.charAt(key * i + j);
            }
            counter++;
        }
    }

    for (int i = 0; i < key; i++) {
        for (int j = 0; j < key; j++) {
            System.out.print(myArray[i][j] + "  ");
        }
        System.out.println();
    }
}

Answer 1

So if I'm understanding this question correctly, you want to create a matrix to hold the characters of an input string, with a minimum size of 4*4?

You're probably better off creating a proper matrix rather than expanding it:

Do you want your matrix to always be square?

1. Get the next-highest (self-inclusive) perfect square using Math.sqrt

    int lowRoot = (int)Math.sqrt(inString.length()); int root; if(lowRoot * lowRoot < inString.length()) root = lowRoot+1; else root = lowRoot; 

2. Create your matrix scaled for your input, minimum four

    int size = (root < 4) ? 4 : root; char[][] matrix = new char[size][size]; 

But if you really want to expand it, you can just create a new matrix of a greater size:

char[][] newMatrix = new char[oldMatrix.length+1][oldMatrix[0].length+1];

And copy the old matrix into the new matrix

for(int i = 0; i < oldMatrix.length; ++i){
    for(int j = 0; j < oldMatrix[i].length; ++j){
        newMatrix[i][j] = oldMatrix[i][j];
    }
}

If you expand by one each time you'll do tons of expands, if you expand by more you might expand too far.

This is really inefficient versus just doing some math at the beginning. Making a properly sized matrix from the start will save you a bunch of loops over your data and regularly having two matrices in memory.

Answer 2

如果您理解正确，那么如果字符串长度大于16，则只需创建一个新数组，然后在一个数组中初始化一个数组列表，如果字符数超过16个，则使用您的数组将一个数组添加到列表中返回数组的方法。