如何在 Java 中减去两个列表/数组的值？

How to subtract values of two lists/arrays in Java?

提问by Voodoothechild

I am working on a Java project and I am having a problem. I want to have the subtract of two lists or arrays a and b in list/array c but I don't know how to do that. I want "a[i] -b[i]" should be in next list c where the value should be c[i]similarly for 5-2=3 any suggestion and help would be appreciated.

我正在处理一个 Java 项目，但遇到了问题。我想在列表/数组 c 中减去两个列表或数组 a 和 b，但我不知道该怎么做。我希望 "a[i] -b[i]" 应该在下一个列表 c 中，其中c[i]5-2=3的值应该类似，任何建议和帮助将不胜感激。

Code:

代码：

public static void l?nge() {
    {
        BufferedReader br = null;
        try {
            br = new BufferedReader(new FileReader(new File("C:\Users/Voodoothechild/Desktop/Pidata/Anfang.txt")));
            String line = null;
            while ((line = br.readLine()) != null) {         
                {
                    BufferedReader bro = null;
                    try {
                        bro = new BufferedReader(new FileReader(new File("C:\Users/Voodoothechild/Desktop/Pidata/Ende.txt")));

                        String lines = null;
                        while ((lines = br.readLine()) != null) {

                            String[] anfang = line.split("\n");
                            String[] ende = lines.split("\n");

                            List<Integer> an = new ArrayList<Integer>();
                            List<Integer> en = new ArrayList<Integer>();

                            for (int index = 0 ; index<ende.length ; index++) {

                                an.add(Integer.parseInt(anfang[index]));
                                en.add(Integer.parseInt(ende[index]));
                                Integer[] anf = new Integer[an.size()];

                                int[] result = new int[anf.length]; 

                                for (int i = 0; i < result.length; i++) { 
                                    result[i] = anf[i] - end[i]; 
                                } 

                            } 
                        }    
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        if (bro != null) {
                            try {
                                bro.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
        } catch(FileNotFoundException e) {
            e.printStackTrace();
        } catch(IOException e) {
            e.printStackTrace();
        } finally {
            if (br != null) {
                try {
                    br.close();
                } catch(IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

回答by Aurora_Titanium

Its pretty straight forward. Before tackling a programming problem. Always do it in steps. Take your problem for example. You need to subtract values from 2 arrays with values.

它非常直接。在解决编程问题之前。始终按步骤进行。以你的问题为例。您需要从 2 个带有值的数组中减去值。

int[] list1 = {4,2,1};

int[] list2 = {2,2,-1};

int[] list1 = {4,2,1};

int[] list2 = {2,2,-1};

Now you have 2 list. Ok next step, write a loop to go through the list. But first make sure that both list have the same length or else you will get an index out of bounce.

现在你有 2 个列表。好的下一步，写一个循环来遍历列表。但首先要确保两个列表具有相同的长度，否则你会得到一个跳出的索引。

for(int i =0; i< list1.length; i++)
    {
      list3[i] = list1[i] - list2[i];
    }

Anyway here is the full answer. Be sure to understand it

无论如何，这里是完整的答案。一定要明白

public class subtract {

公共课减法{

  public static void main(String[] args)
  {
    int[] list1 = {4,2,1};
    int[] list2 = {2,2,-1};
    int[] list3 = new int[list1.length];

    //Looping the list
    for(int i =0; i< list1.length; i++)
    {
      list3[i] = list1[i] - list2[i];
    }

    //Print Statement
    for(int j =0; j< list3.length; j++)
    {
      System.out.println(list3[j]);
    }
  }

}

}

回答by Grzegorz Piwowarek

It can be done easily using Stream API:

使用 Stream API 可以轻松完成：

int[] list1 = {4,2,1};
int[] list2 = {2,2,-1};

IntStream.range(0, list1.length)
  .mapToObj(i -> list1[i] - list2[i])
  .collect(Collectors.toList());

or even easier using Javaslang:

甚至更容易使用 Javaslang：

Stream.range(0, list1.length)
  map(i -> list1[i] - list2[i]);

or by zipping two lists together:

或者将两个列表压缩在一起：

List.ofAll(list1)
  .zip(List.ofAll(list2))
  .map(t -> t._1 - t._2);

回答by m4heshd

Here's a very simple answer you can apply to your program.

这是一个非常简单的答案，您可以将其应用到您的程序中。

public static void main(String[] args) {
    int[] a = new int[4];
    int[] b = new int[4];
    int[] c = new int[4];

    a[0] = 5;
    a[1] = 12;
    a[2] = 20;
    a[3] = 50;
    b[0] = 1;
    b[1] = 2;
    b[2] = 3;
    b[3] = 4;

    for(int i=0; i<a.length; i++){
       c[i] = a[i] - b[i];
        System.out.println(c[i]);
    }
}

回答by jlbofh

The answer is the method removeAllof class Collection

答案是Collection类的removeAll方法

ArrayList<Integer> s1 = new ArrayList<Integer>(Arrays.asList(a1));
ArrayList<Integer> s2 = new ArrayList<Integer>(Arrays.asList(a2));
s1.removeAll(s2);
Integer[] result = s1.toArray(new Integer[s1.size()]);