Java 8 Check if Array Contains a Certain Value Example

1. Introduction

An array is a data structure which holds a fixed number of values of a single type. In this example, I will demonstrate how to check if an array contains a certain value in three ways:

• Convert an array to a Collection and check with the contains method
• Use Arrays.binarySearch to check when the array is sorted
• Convert an array to Java 8 Stream and check with anyMatch, filter, or findAny methods

2. Technologies used

The example code in this article was built and run using:

• Java 1.8.101
• Maven 3.3.9
• Eclipse Oxygen
• JUnit 4.12

3. Maven Project

3.1 Dependency

Add JUnit to the pom.xml.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>zheng.jcg.demo</groupId>
	<artifactId>java8-demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
			<scope>test</scope>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.3</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

3.2 Sample Data

I will create a SampleData class which has the equals method. This class will be used to form an object array.

SampleData.java

package com.zheng.demo;

public class SampleData {

	private int key;
	private String name;

	public SampleData(int key, String name) {
		super();
		this.key = key;
		this.name = name;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		SampleData other = (SampleData) obj;
		if (key != other.key)
			return false;
		return true;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + key;
		return result;
	}

	@Override
	public String toString() {
		return "SampleData [key=" + key + ", name=" + name + "]";
	}

}

3.3 Check Item from Array with Stream

JDK 8 Stream interface provides three methods that we can use to check an item from an array.

In this step, I will create a CheckItemFromArray_Java8 class to demonstrate how to check an item in an array.

CheckItemFromArray_Java8.java

package com.zheng.demo;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;

public class CheckItemFromArray_Java8 {

	public boolean byDoubleStreamAnyMatch(double[] values, double targetValue) {
		return DoubleStream.of(values).anyMatch(x -> x == targetValue);
	}

	public boolean byDoubleStreamAnyMatch_2(double[] values, double targetValue) {
		return DoubleStream.of(values).anyMatch(x -> Double.compare(x, targetValue) == 0);
	}

	public boolean byIntStreamAnyMatch(int[] values, int targetValue) {
		return IntStream.of(values).anyMatch(x -> x == targetValue);
	}

	public boolean byLongStreamAnyMatch(long[] values, long targetValue) {
		return LongStream.of(values).anyMatch(x -> x == targetValue);
	}

	public <T> boolean byStreamAnyMatch(T[] array, T targetValue) {
		return Arrays.stream(array).anyMatch(targetValue::equals);
	}

	public boolean byStreamAnyMatchEquals(String[] checkingArray, String targetValue) {
		return Arrays.stream(checkingArray).anyMatch(targetValue::equals);
	}

	public boolean byStreamAnyMatchEqualsIgnoreCase(String[] checkingArray, String targetValue) {
		return Arrays.stream(checkingArray).anyMatch(targetValue::equalsIgnoreCase);
	}

	public boolean byStreamFilter(String[] checkingArray, String targetValue) {
		List<String> filterData = Arrays.stream(checkingArray).filter(x -> targetValue.equals(x))
				.collect(Collectors.toList());
		return !filterData.isEmpty();
	}

	public boolean byStreamFindAny(int[] values, int targetValue) {
		int found = Arrays.stream(values).filter(x -> targetValue == x).findAny().orElse(-1);
		return found != -1;
	}
	

	public boolean byStreamFindAny(String[] checkingArray, String targetValue) {
		String found = Arrays.stream(checkingArray).filter(x -> targetValue.equals(x)).findAny().orElse(null);
		return found != null;
	}
}

Note: the equality check is different based on the object type.

4. JUnit Tests

4.1 Test Data Provider

I will create a TestDataProvider class for the common data.

TestDataProvider.java

package com.zheng.demo;

public class TestDataProvider {

	public static double[] DOUBLE_ARRAY = new double[] { 1d, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
	public static int[] INT_ARRAY = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
	public static long[] LONG_ARRAY = new long[] { 1l, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
	public static final int NOT_IN_INT_ARRAY = 20;
	public static String[] STRING_ARRAY = new String[] { "AA", "BB", "CC", "DD", "EE" };
	public static final String STRING_NOT_IN_ARRAY = "D";

	public static SampleData[] getSampleDataArray() {
		SampleData[] objects = new SampleData[4];
		objects[0] = new SampleData(1, "Mary");
		objects[1] = new SampleData(2, "Terry");
		objects[2] = new SampleData(3, "Tom");
		objects[3] = new SampleData(4, "John");
		return objects;
	}
}

4.2 Check Item from Array with Arrays

java.util.Arrays class provides binarySearch which finds the specified element using the binary search algorithm.

I will create an ArraysBinarySearchTest class to search an item.

ArraysBinarySearchTest.java

package com.zheng.demo;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;
import java.util.Collections;

import org.junit.Test;

public class ArraysBinarySearchTest {

	@Test
	public void findfrom_sorted_double_Array() {
		for (double item : TestDataProvider.DOUBLE_ARRAY) {
			int foundIndex = Arrays.binarySearch(TestDataProvider.DOUBLE_ARRAY, item);
			assertTrue(foundIndex >= 0);
		}
	}

	@Test
	public void findfrom_sorted_int_Array() {
		for (int item : TestDataProvider.INT_ARRAY) {
			int foundIndex = Arrays.binarySearch(TestDataProvider.INT_ARRAY, item);
			assertTrue(foundIndex >= 0);
		}
	}

	@Test
	public void findfrom_sorted_long_Array() {
		for (long item : TestDataProvider.LONG_ARRAY) {
			int foundIndex = Arrays.binarySearch(TestDataProvider.LONG_ARRAY, item);
			assertTrue(foundIndex >= 0);
		}
	}

	@Test
	public void findfrom_sorted_String_Array() {
		String[] stringArray = TestDataProvider.STRING_ARRAY;
		Collections.sort(Arrays.asList(stringArray));
		int foundIndex = Arrays.binarySearch(stringArray, TestDataProvider.STRING_NOT_IN_ARRAY);
		assertFalse(foundIndex >= 0);

		for (String item : stringArray) {
			foundIndex = Arrays.binarySearch(stringArray, item);
			assertTrue(foundIndex >= 0);
		}
	}

}

4.3 Check Item from Array with Collection

java.util.Collection interface provides contains(Object o) which returns true if this collection contains the specified element.

I will create a CollectionContainsTest class to convert an array into a List or Set and use thecontains method to check if an array contains a certain value.

CollectionContainsTest.java

package com.zheng.demo;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import org.junit.Before;
import org.junit.Test;

public class CollectionContainsTest {

	private String[] stringArray;

	@Before
	public void setup() {
		stringArray = TestDataProvider.STRING_ARRAY;
	}

	@Test
	public void check_byListContains() {
		boolean found = Arrays.asList(stringArray).contains(TestDataProvider.STRING_NOT_IN_ARRAY);
		assertFalse(found);

		for (String item : stringArray) {
			found = Arrays.asList(stringArray).contains(item);
			assertTrue(found);
		}
	}

	@Test
	public void check_bySetContains() {
		Set set = new HashSet(Arrays.asList(stringArray));
		boolean found = set.contains(TestDataProvider.STRING_NOT_IN_ARRAY);
		assertFalse(found);

		for (String item : stringArray) {
			found = set.contains(item);
			assertTrue(found);
		}
	}

}

4.4 Test for CheckItemFromArray_Java8

In this step, I will create CheckItemFromArray_Java8Test to test the methods defined in CheckItemFromArray_Java8.

CheckItemFromArray_Java8Test.java

package com.zheng.demo;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;

import org.junit.Before;
import org.junit.Test;

public class CheckItemFromArray_Java8Test {

	private CheckItemFromArray_Java8 testObject = new CheckItemFromArray_Java8();

	private int[] intValues;
	private long[] longValues;
	private double[] doubleValues;
	private String[] checkingArray;

	@Before
	public void setup() {
		checkingArray = TestDataProvider.STRING_ARRAY;
		intValues = TestDataProvider.INT_ARRAY;
		longValues = TestDataProvider.LONG_ARRAY;
		doubleValues = TestDataProvider.DOUBLE_ARRAY;
	}

	@Test
	public void byStreamAnyMatchEqualsIgnoreCase() {
		boolean found = testObject.byStreamAnyMatchEqualsIgnoreCase(checkingArray,
				TestDataProvider.STRING_NOT_IN_ARRAY);
		assertFalse(found);

		Arrays.stream(checkingArray)
				.forEach(x -> assertTrue(testObject.byStreamAnyMatchEqualsIgnoreCase(checkingArray, x)));
	}

	@Test
	public void byStreamAnyMatchEquals() {
		boolean found = testObject.byStreamAnyMatchEquals(checkingArray, TestDataProvider.STRING_NOT_IN_ARRAY);
		assertFalse(found);

		Arrays.stream(checkingArray).forEach(x -> assertTrue(testObject.byStreamAnyMatchEquals(checkingArray, x)));
	}

	@Test
	public void byStreamFilter() {
		boolean found = testObject.byStreamFilter(checkingArray, TestDataProvider.STRING_NOT_IN_ARRAY);
		assertFalse(found);

		Arrays.stream(checkingArray).forEach(x -> assertTrue(testObject.byStreamFilter(checkingArray, x)));
	}

	@Test
	public void byStreamFindAny() {
		boolean found = testObject.byStreamFindAny(checkingArray, TestDataProvider.STRING_NOT_IN_ARRAY);
		assertFalse(found);

		Arrays.stream(checkingArray).forEach(x -> assertTrue(testObject.byStreamFindAny(checkingArray, x)));
	}

	@Test
	public void test_byAnyMatch() {
		SampleData[] objects = TestDataProvider.getSampleDataArray();

		boolean found = testObject.byStreamAnyMatch(objects, new SampleData(1, "Mary"));
		assertTrue(found);

		found = testObject.byStreamAnyMatch(objects, new SampleData(6, "Mary"));
		assertFalse(found);
	}

	@Test
	public void checkInt_byStreamAnyMatch() {
		IntStream.of(intValues).forEach(x -> assertTrue(testObject.byIntStreamAnyMatch(intValues, x)));
		boolean found = testObject.byIntStreamAnyMatch(intValues, TestDataProvider.NOT_IN_INT_ARRAY);
		assertFalse(found);
	}

	@Test
	public void checkLong_byStreamAnyMatch() {
		boolean found = testObject.byLongStreamAnyMatch(longValues, TestDataProvider.NOT_IN_INT_ARRAY);
		assertFalse(found);

		LongStream.of(longValues).forEach(x -> assertTrue(testObject.byLongStreamAnyMatch(longValues, x)));
	}

	@Test
	public void checkDouble_byStreamAnyMatch() {
		boolean found = testObject.byDoubleStreamAnyMatch(doubleValues, TestDataProvider.NOT_IN_INT_ARRAY);
		assertFalse(found);

		DoubleStream.of(doubleValues).forEach(x -> assertTrue(testObject.byDoubleStreamAnyMatch(doubleValues, x)));
	}

	@Test
	public void checkDouble_byStreamAnyMatch_2() {
		boolean found = testObject.byDoubleStreamAnyMatch_2(doubleValues, TestDataProvider.NOT_IN_INT_ARRAY);
		assertFalse(found);

		DoubleStream.of(doubleValues).forEach(x -> assertTrue(testObject.byDoubleStreamAnyMatch(doubleValues, x)));
	}

	@Test
	public void byStreamFindAny_withInt() {
		boolean found = testObject.byStreamFindAny(intValues, TestDataProvider.NOT_IN_INT_ARRAY);
		assertFalse(found);

		IntStream.of(intValues).forEach(x -> assertTrue(testObject.byStreamFindAny(intValues, x)));

	}

}

5. Demo

Execute mvn clean install and capture the output:

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Tests Output

C:\gitworkspace\java8-demo>mvn clean install
[INFO] Scanning for projects...
[INFO]
[INFO] ---------------------< zheng.jcg.demo:java8-demo >----------------------
[INFO] Building java8-demo 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ java8-demo ---
[INFO] Deleting C:\gitworkspace\java8-demo\target
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ java8-demo ---
[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources,i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.3:compile (default-compile) @ java8-demo ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding Cp1252, i.e. build is platform dependent!
[INFO] Compiling 2 source files to C:\gitworkspace\java8-demo\target\classes
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ java8-demo ---
[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources,i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.3:testCompile (default-testCompile) @ java8-demo ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding Cp1252, i.e. build is platform dependent!
[INFO] Compiling 4 source files to C:\gitworkspace\java8-demo\target\test-classes
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ java8-demo ---
[INFO] Surefire report directory: C:\gitworkspace\java8-demo\target\surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.zheng.demo.ArraysBinarySearchTest
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.058 sec
Running com.zheng.demo.CheckItemFromArray_Java8Test
Tests run: 10, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.051 sec
Running com.zheng.demo.CollectionContainsTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 16, Failures: 0, Errors: 0, Skipped: 0

[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ java8-demo ---
[INFO] Building jar: C:\gitworkspace\java8-demo\target\java8-demo-0.0.1-SNAPSHOT.jar
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ java8-demo ---
[INFO] Installing C:\gitworkspace\java8-demo\target\java8-demo-0.0.1-SNAPSHOT.jar to C:\repo\zheng\jcg\demojava8-demo\0.0.1-SNAPSHOT\java8-demo-0.0.1-SNAPSHOT.jar
[INFO] Installing C:\gitworkspace\java8-demo\pom.xml to C:\repo\zheng\jcg\demo\java8-demo\0.0.1-SNAPSHOT\java8-demo-0.0.1-SNAPSHOT.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5.727 s
[INFO] Finished at: 2018-11-08T09:50:35-06:00
[INFO] ------------------------------------------------------------------------

C:\gitworkspace\java8-demo>

6. Summary

In this example, we demonstrated how to check if an array contains a certain value using Java 8 Stream interface as well as the Collection’s contains method.

7. Download the Source Code

This example consists of a Maven project to check if an array contains a certain value.

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