String/Object in Array Testing in Java – using Arrays.asLi

  • 时间：2020-10-07 14:38:56
  • 分类：网络文摘
  • 阅读：150 次

This tutorial presents three ways of testing if a given element (integer, doubles, objects, strings) is in a given Array using Java programming language.

2091E060-120E-4C44-BAA3-7E4E0DF7BD55 String/Object in Array Testing in Java - using Arrays.asList and Arrays.Stream Parallel java

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):

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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:

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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:

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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!

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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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