如何在Java中逐元素地比较两个数组？

Question

I have two arrays of objects in Java, which contain some fields that I need to compare, but the thing is I need to compare element by element, that means, that I want the compare a field from the first object in my first array with the first object in my second array, my second object from the first array with my second object from the second array and so on. This is what I have done so far, but the idea is that I do not know what should be the limit for my second array. From my point of view the second array should start from the index of the first array like this:

for(int i = 0; i < resultEntries.size(); i++) {
    for(int j = i; j < resultColorEntries.size(); j++) {
        if(resultEntries.get(i).getColor())...
    };
}

Another solution or a solution to my problem would be welcome. Thanks in advance!

Answer 1

如果你想更有效地与O（N）进行比较，你需要实现你的对象hash（），并将你的项添加到一个hashset，例如arrayA的arraySet和arrayB的hashsetB，然后比较这两个hashsets。

Answer 2

You don't have to make 2 loops, you can achieve this only with one:

for(int i = 0; i < resultEntries.size() && i < resultColorEntries.size(); i++) {
    if(resultEntries.get(i).getColor().equals(resultColorEntries.get(i).getColor()) {
         // Same!
    }
}

Answer 3

that I want the compare a field from the first object in my first array with the first object in my second array, my second object from the first array with my second object from the second array and so on

You shouldn't have to write nested loop then. One loops will do.

Codes should be

for(int i=0;i<resultEntries.size();i++){

 if(resultEntries.get(i).getColor().equals(resultColorEntries.get(i).getColor()) )...

Assuming you have the same size of lists.

Answer 4

You can keep check of index that it is less than the size of both arrays.

for(int i=0;i<resultEntries.size() && i<resultColorEntries.size();i++){
             if(resultEntries.get(i).getColor()) {
             }
     }

Answer 5

The whole thing only makes sense when both arrays have equal dimensions; so you could go for:

Whatever a[] = ...
Somthinelse b[] = ...

check for equal length

for (int i=0; i < a.length; i++) {
  if (a[i].whatever.equals(b[i].whatever))...

Point is: no need for two loops!

But: there is no nice way of generalizing that (like: writing a method that compares those arrays; but on different fields for example). Well, you could use method references, and using method references, ending up with something like

public void compareArraysOn(Whatever[] a, Other[] b, Function<T,U> extractorForA, ...) {

that could be called like compareArraysOn(a, b, Whatever::getColor(), SomethinElse::getColor())