gpt4 book ai didi

java - Equals 方法不适用于两个相同的对象

转载 作者:行者123 更新时间:2023-12-03 23:42:25 24 4
gpt4 key购买 nike

我编写了一个代码来查找唯一的图像。如果两个图像具有相同的名称(即使扩展名不同)并且大小相等(宽度 * 长度),则它们相等。
但它未能找到独特的图像。
即使在覆盖 equals 方法之后,HashSet 方法也无法识别两个相似的对象。

    import java.util.*;

class UniqueImages {
public static class Image {
private String filename;
private int width;
private int height;
public Image(String filename, int width, int height) {
this.filename = filename;
this.width = width;
this.height = height;
}


@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((filename == null) ? 0 : filename.hashCode());
result = prime * result + height;
result = prime * result + width;
return result;
}

/**
* Two Images are considered equal if they have
* the same filename (without the extension), and the
* same number of pixels.
* Thus, flag.jpg with width=60 height=40 is
* equal to flag.gif with width=40 and height=60
*/
public boolean equals(Object other) {
Image o = (Image)other;
if (filename == null || o.filename == null)
return false;
String[] components = filename.split("\\.");
String[] ocomponents = o.filename.split("\\.");
return components[0].equals(ocomponents[0]) &&
width * height == o.width * o.height;
}

public String toString() {
return "Image: filename=" + filename + " Size=" + width*height;
}
}

public static void printImages(Set<Image> images) {
for(Image image: images) {
System.out.println(image);
}
}

public static void main(String[] args) {
Image[] images = {new Image("flag.jpg", 40, 60),
new Image("flag.gif", 40, 60),
new Image("smile.gif", 100, 200),
new Image("smile.gif", 50, 400),
new Image("other.jpg", 40, 60),
new Image("lenna.jpg", 512, 512),
new Image("Lenna.jpg", 512, 512)};

Set<Image> set = new HashSet<Image>(Arrays.asList(images));
UniqueImages.printImages(set);
}
}

最佳答案

如果您的 equals() 认为具有相同总大小的两个图像相等方法(即使它们不具有相同的 widthheight ),它们也应该具有相同的 hashCode() .
但这不是唯一的问题。你也应该改 hashCode()忽略文件名后缀,以适应 equals() 的实现.

public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((filename == null) ? 0 : filename.split("\\.")[0].hashCode());
result = prime * result + (height * width);
return result;
}
有了这两个变化, HashSet将消除两个重复项,导致:
Image: filename=smile.gif Size=20000
Image: filename=flag.jpg Size=2400
Image: filename=lenna.jpg Size=262144
Image: filename=other.jpg Size=2400
Image: filename=Lenna.jpg Size=262144

关于java - Equals 方法不适用于两个相同的对象,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/64953134/

24 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com