This tutorial presents three ways of testing if a given element (integer, doubles, objects, strings) is in a given Array using Java programming language.
Java
Java’s Naive Implementation of Element (String) In Array Tests using Generic
In Java, if we want to test a given element in array, we can implement a naive version (let’s take String for example):
1 2 3 4 5 6 | private static boolean stringInArray1(String str, String[] arr) { for (var x: arr) { if (x.equals(str)) return true; } return false; } |
private static boolean stringInArray1(String str, String[] arr) {
for (var x: arr) {
if (x.equals(str)) return true;
}
return false;
}If we want to go with generic type, we can of course:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | package com.helloacm; public class Main<T> { private boolean inArray(T val, T[] arr) { for (T x: arr) { if (x.equals(val)) return true; } return false; } public static void main(String[] args) { var arr = new String[] {"a", "ab", "abc", "abcde"}; var test = new Main<String>(); System.out.println(test.inArray(null, arr)); System.out.println(test.inArray("adfasd", arr)); System.out.println(test.inArray("a", arr)); } } |
package com.helloacm;
public class Main<T> {
private boolean inArray(T val, T[] arr) {
for (T x: arr) {
if (x.equals(val)) return true;
}
return false;
}
public static void main(String[] args) {
var arr = new String[] {"a", "ab", "abc", "abcde"};
var test = new Main<String>();
System.out.println(test.inArray(null, arr));
System.out.println(test.inArray("adfasd", arr));
System.out.println(test.inArray("a", arr));
}
}In-Array Test using Arrays.AsList().contains
We can convert the array type to List using Arrays.asList then in this case, we can simply use its contain method:
1 2 3 | private boolean stringInArray1(T val, T[] arr) { return Arrays.asList(arr).contains(val); } |
private boolean stringInArray1(T val, T[] arr) {
return Arrays.asList(arr).contains(val);
}Parallel version of Element-In-Array Tests using Arrays.Stream
Even better, we can convert the array to stream, then make a parallel version of the in-array test. It is cool, and it’s potentially faster!
1 2 3 4 5 | private boolean stringInArray1(T val, T[] arr) { return Arrays.stream(arr). parallel(). anyMatch(s -> s.equals(val)); } |
private boolean stringInArray1(T val, T[] arr) {
return Arrays.stream(arr).
parallel().
anyMatch(s -> s.equals(val));
}–EOF (The Ultimate Computing & Technology Blog) —
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