将一个整数数组列表与另一个整数数组列表相加，给出错误:预期变量 [英] Summing one ArrayList of Integers to another ArrayList of Integers, gives error: variable expected

问题描述

我的 Android 应用程序中有两个 6 个元素的 ArrayList.我们称它们为 ArrayListA"和B".我的类中的每个对象在构造函数中都有这一行:

I have two ArrayList of 6 elements in my Android application. Let's call them ArrayList "A" and "B". Each object in my class has this line in the constructor:

likes = new ArrayList<Integer>();

我也可以在构造函数中添加这一行(我不确定哪个更好，但我想将大小初始化为 6，并且所有元素都应为 0):

I could also add this line in the constructor (I'm not sure which one is better, but I want to initialize the size to 6, and all elements should be 0):

likes = new ArrayList<>(Collections.nCopies(6, 0));

我的类中有一个名为Calculate 的方法，该方法应该采用与A 大小相同的整数B 的新ArrayList 作为参数.然后将 B 与该对象的 ArrayList, A 相加/求和.

I have a method in my class called Calculate, which is supposed to take a new ArrayList of Integers, B, of the same size as A, as a parameter. Then add / sum B with this object's ArrayList, A.

方法如下:

public void Calculate(ArrayList<Integer> likes){
    for(int i = 0; i < likes.size(); i++){
        this.likes.get(i) += likes.get(i);
        //this.likes.get(i) = 3;
    }
}

我在 this.likes.get(i) 下方看到一条红线，说:

I'm getting a red line under the line this.likes.get(i), saying:

预期变量

即使我试着说 this.likes.get(i) = 3; 我也会得到同样的错误.

Even if I try to just say this.likes.get(i) = 3; I get the same error.

假设 A = {0,0,0,0,0,0}，B = {1,0,0,-1,1,0}

Let's say A = {0,0,0,0,0,0}, and B = {1,0,0,-1,1,0}

对 ArrayList 求和以使 A = {1,0,0,-1,1,0} 的正确方法是什么?

What is the correct way to sum to ArrayList, to make A = {1,0,0,-1,1,0}?

推荐答案

您不能为 this.likes.get(i) 之类的值赋值.您只能为变量赋值.

You can't assign a value to a value such as this.likes.get(i). You can only assign values to variables.

要修改 ArrayList 的 i'th 元素，您应该使用 ArrayList 的 set 方法:

To modify the i'th element of an ArrayList you should use the ArrayList's set method:

this.likes.set(i,this.likes.get(i) + likes.get(i));

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