如何将两个 arrays 中的常用词保存到第三个数组中？

Question

I am trying to save all common words from arr1 and arr2 and then store to arr3.

String[] arr1 = {"pEace", "happiness", "Gives", "So", "aaa"};
String[] arr2 = {"pEace", "HappiNess", "joy", "give", "AAA", "enjoy", "learN"};

int k = 0;
String[] arr3 = new String[0];
for (int i = 0; i < arr1.length; i++) {
    for (int j = 0; j < arr2.length; j++) {
        if (arr1[i].equalsIgnoreCase(arr2[j])) {
            System.out.println(arr1[i]);
            arr3[k] = arr1[i];
            k++;
        }
    }
}
System.out.println(Arrays.toString(arr3));

Answer 1

The init size of arr3 is 0

String[] arr3 = new String[0];

You should init with size is total length of arr1 and arr2 or use ArrayList . On that example are 12

Answer 2

You can convert these arrays to collections and then use the retainAll method. It works differently in different collections.

Try it online!

// Convert arrays to collections
String[] arr1 = {"pEace", "happiness", "Gives", "So", "aaa", "learn"};
String[] arr2 = {"pEace", "HappiNess", "joy", "give", "AAA", "learN"};

Collection<String> coll1 = Arrays.asList(arr1);
Collection<String> coll2 = Arrays.asList(arr2);

// ArrayList
ArrayList<String> list1 = new ArrayList<>();
ArrayList<String> list2 = new ArrayList<>();

list1.addAll(coll1);
list2.addAll(coll2);

list2.retainAll(list1);

System.out.println(list2); // [pEace]

// TreeSet
TreeSet<String> set1 = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
TreeSet<String> set2 = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);

set1.addAll(coll1);
set2.addAll(coll2);

set2.retainAll(set1);

System.out.println(set2); // [AAA, HappiNess, learN, pEace]

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^{See also: Is it possible that TreeSet equals HashSet but not HashSet equals TreeSet}