Java program to implement the conversion between array (Array) and set (HashSet)

Java Comprehensive Examples

In this program, you will learn how to implement the conversion between array (Array) and set (HashSet) in a Java program.

Example1: Convert array to set

import java.util.*;
public class ArraySet {
　　　　public static void main(String[] args) {
　　　　　　　　String[] array = {"a", "b", "c"};
　　　　　　　　Set<String> set = new HashSet<>(Arrays.asList(array));
　　　　　　　　System.out.println("Set: " );　+　set);
　　　　}
}

When running the program, the output is:

Set: [a, b, c]

In the above program, we have an array named array. To convert the array to a set, first use asList() to convert it to a list, because HashSet accepts list as a constructor

Then, we use the elements of the converted list to initialize the set

Example2: Use stream to convert array to Set

import java.util.*;
public class ArraySet {
　　　　public static void main(String[] args) {
　　　　　　　　String[] array = {"a", "b", "c"};
　　　　　　　　Set<String> set = new HashSet<>(Arrays.stream(array).collect(Collectors.toSet()));
　　　　　　　　System.out.println("Set: " );　+　set);
　　　　}
}

The output of the program is similar to the example1The same.

In the above program, it is not the case that the array is first converted to a list and then to a set, but the array is converted to a set using a stream

We first use the stream() method to convert the array to a stream, and then use the collect() method with toSet() as a parameter to convert the stream to a set

Example3Convert Collection to Array

import java.util.*;
public class SetArray {
　　　　public static void main(String[] args) {
　　　　　　　　Set<String> set = new HashSet<>();
　　　　　　　　set.add("a");
　　　　　　　　set.add("b");
　　　　　　　　set.add("c");
　　　　　　　　String[] array = new String[set.size()];
　　　　　　　　set.toArray(array);
　　　　　　　　System.out.println("Array:  ",　+　Arrays.toString(array));
　　　　}
}

When running the program, the output is:

Array:  [a, b, c]

In the above program, we have a HashSet named set. To convert set to an array, we first create an array of the same length as set and use the toArray() method.

Java Comprehensive Examples