java - 错误不兼容类型 : possible lossy conversion from double to long?

Question

我制作的游戏出现问题。当尝试编译代码时，我收到一个奇怪的错误，即这篇文章的标题。任何关于它可能意味着什么的帮助。它告诉我要查看的错误是我尝试调用绘图线程的位置。抛出错误的代码是 -- Try Thread.sleep(time);

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class Stacker
  extends JFrame
  implements KeyListener
{
  int iteration = 1;
  static double time = 200.0D;
  static int last = 0;
  static int m = 10;
  static int n = 20;
  JLabel[][] b;
  static int[] length = { 5, 5 };
  static int layer = 19;
  static int[] deltax = new int[2];
  static boolean press = false;
  static boolean forward = true;
  static boolean start = true;

  public static void main(String[] args)
  {
    System.setProperty("java.util.Arrays.useLegacyMergeSort", "true");
    new Stacker();
  }

  public Stacker()
  {
    setDefaultCloseOperation(3);
    this.b = new JLabel[m][n];
    setLayout(new GridLayout(n, m));
    for (int y = 0; y < n; y++) {
      for (int x = 0; x < m; x++)
      {
        this.b[x][y] = new JLabel(" ");
        this.b[x][y].setBackground(Color.white);
        add(this.b[x][y]);
        this.b[x][y].setEnabled(true);
        this.b[x][y].setOpaque(true);
        this.b[x][y].setBorder(BorderFactory.createLineBorder(Color.GRAY));
        this.b[x][y].setPreferredSize(new Dimension(40, 30));
      }
    }
    setFocusable(true);
    addKeyListener(this);
    pack();
    setVisible(true);
    go();
  }

  public void go()
  {
    int tmp = 0;
    Component temporaryLostComponent = null;
    do
    {
      if (forward) {
        forward();
      } else {
        back();
      }
      if (deltax[1] == 10 - length[1]) {
        forward = false;
      } else if (deltax[1] == 0) {
        forward = true;
      }
      draw();
      try
      {
        Thread.sleep(time);
      }
      catch (InterruptedException e)
      {
        e.printStackTrace();
      }
    } while (!

      press);
    if (layer > 12) {
      time = 150 - (this.iteration * this.iteration * 2 - this.iteration);
    } else {
      time -= 2.2D;
    }
    this.iteration += 1;
    layer -= 1;
    press = false;
    tmp = check();
    length[0] = length[1];
    length[1] = tmp;
    if ((layer == -1) && (length[1] > 0))
    {
      JOptionPane.showMessageDialog(temporaryLostComponent, "Congratulations! You beat the game!");
      System.exit(0);
    }
    if (length[1] <= 0)
    {
      JOptionPane.showMessageDialog(temporaryLostComponent, "Game over! You reached line " + (18 - layer) + "!");
      System.exit(0);
    }
    last = deltax[1];
    start = false;
    go();
  }

  public int check()
  {
    if (start) {
      return length[1];
    }
    if (last < deltax[1])
    {
      if (deltax[1] + length[1] - 1 <= last + length[0] - 1) {
        return length[1];
      }
      return length[1] - Math.abs(deltax[1] + length[1] - (last + length[0]));
    }
    if (last > deltax[1]) {
      return length[1] - Math.abs(deltax[1] - last);
    }
    return length[1];
  }

  public void forward()
  {
    deltax[0] = deltax[1];
    deltax[1] += 1;
  }

  public void back()
  {
    deltax[0] = deltax[1];
    deltax[1] -= 1;
  }

  public void draw()
  {
    for (int x = 0; x < length[1]; x++) {
      this.b[(x + deltax[0])][layer].setBackground(Color.white);
    }
    for (int x = 0; x < length[1]; x++) {
      this.b[(x + deltax[1])][layer].setBackground(Color.BLUE);
    }
  }

  public void keyPressed(KeyEvent e)
  {
    if (e.getKeyCode() == 32) {
      press = true;
    }
  }

  public void keyReleased(KeyEvent arg0) {}

  public void keyTyped(KeyEvent arg0) {}
}

Answer 1

这是一个标准的 Java 编译器错误，旨在防止程序员意外使用精度较低的类型。在您的情况下，您尝试将十进制值( double )传递到采用整数类型的方法中(Thread.sleep(milliseconds))

double value = 1.234;
Thread.sleep(value); // Error, value passed would end up being 1, not 1.234
Thread.sleep((long)value); // OK, you've explicity made the cast from 1.234 to 1 yourself

强烈建议您阅读 Java 类型，例如official tutorial .