java - 返回数组元素的长度

Question

嗨，我想知道是否可以获取数组元素的长度？我查看了 java 文档，我看到的唯一可检索的长度是数组本身的长度。我的任务是使用元素的长度来随机化我的砖 block 的颜色。如果有人能够指出获取元素长度的正确方向，我们将不胜感激。这是我的代码:

import javax.swing.JFrame;
import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;

@SuppressWarnings("serial")
public class legos2v2 extends JFrame {
private int startX;
private int startY;
private int legoWidth;
private int legoHeight;
private int baseLength;
private int arcWidth;
private int arcHeight;
private Color[] colors;

// Constructor
public legos2v2() {
    super("Jimmy's LEGOs");
    startX = 20;
    startY = 300;
    legoWidth = 50;
    legoHeight = 20;
    baseLength = 10;
    arcWidth = 2;
    arcHeight = 2;


    // Declare and Array of Colors
    Color[] colors = {Color.red, Color.blue, Color.yellow, Color.green,
            Color.pink, Color.black, Color.magenta, Color.orange,
            Color.cyan};


    // Get length of color
    System.out.println("Array Length = " + colors.length + "\n");

}
// The drawings in the graphics context
public void paintComponent(Graphics g) {


    // Call the paint method of the JFrame
    super.paint(g);

    int currentX = startX;
    int currentY = startY;

    Random random = new Random();


    // row = 0 is the bottom row
    for (int row = 1; row <= baseLength; row++) {
        currentX = startX;

        for (int col = 0; col <= baseLength - row; col++) {

            g.fillRoundRect(currentX, currentY, legoWidth, legoHeight, arcWidth, arcHeight);


            // Generate random integer from 0 to 8
            int randomIndex = random.nextInt(colors.length);


            g.setColor(this.colors[randomIndex]);
            //Error here   this.colors = colors[randomIndex];



            // Print random integers to screen
            System.out.println(randomIndex);

            currentX = currentX + legoWidth;
        }
        currentY -= legoHeight;
        startX += legoWidth / 2;
    }
}
// The main method
public static void main(String[] args) {
    legos2v2 app = new legos2v2();
    // Set the size and the visibility
    app.setSize(550, 325);
    app.setVisible(true);
    // Exit on close is clicked
    app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

Answer 1

老师要求你做的就是我在评论中说的:

1. 初始化颜色数组:

   Color[] colors = ...;
   

2. 生成一个介于 0(含)和数组长度(不含:)之间的随机整数

   int randomIndex = random.nextInt(colors.length);
   

   这将返回一个整数，它是颜色数组的有效索引。

3. 在随机索引处选择颜色:

    Color color = colors[randomIndex];
   

这避免了使用丑陋的 if block 链来生成随机颜色。

编辑:

1. 将 Color[] colors = 替换为 this.colors = 以初始化实例变量，而不是重新定义同名的局部变量
2. 正如其他评论中告诉您的那样，将 Random random = new Random(); 移到第一个 for 循环之前
3. 正如其他注释中告诉您的那样，重写 paintComponent() 而不是重写 paint()。