java - 如何优化java中的嵌套for循环？

Question

for (int i = 0 ; i < row ; i++){
        for (int k = 0 ; k < col ; k++) {
            System.out.print("\t" + mat[i][k]);
        }

My objective is to reduce the execution time for a large value of rows and cols

Answer 1

我没想到会这样，但埃利奥特的评论是正确的。巴希尔，您要求提供一个示例，如下:

public class Main
{

    private static void test()
    {
        int row = 1000;
        int col = 1000;
        int mat[][] = new int[row][col];

        StringBuilder buffer=new StringBuilder();

        for (int i = 0; i < row; i++)
        {
            for (int k = 0; k < col; k++)
            {
                //System.out.print("\t" + mat[i][k]);

                //System.out.print('\t');                
                //System.out.print(mat[i][k]);

                buffer.append('\t');
                buffer.append(mat[i][k]);
            }
        }
        System.out.println(buffer.toString());
    }

    public static void main(String[] args)
    {
        long start = System.currentTimeMillis();
        test();
        long end = System.currentTimeMillis();
        System.err.println("Test took " + (end - start) + "ms");
    }
}

我在命令行中执行了它(在 Linux 上)，以确保我的终端窗口或显卡的性能不会影响测量:

java Main > /dev/null

缓冲版本的运行速度比原始版本快 30 倍。