Given a set (HashSet or TreeSet) of strings in Java, convert it into an array of strings.
Input : Set hash_Set = new HashSet(); hash_Set.add("Geeks"); hash_Set.add("For"); Output : String arr[] = {"Geeks", "for"}
Method 1 (Simple)
We simply create an empty array. We traverse the given set and one by one add elements to the array.
// Java program to demonstrate conversion of // Set to array using simple traversal import java.util.*;
class Test {
public static void main(String[] args)
{
// Creating a hash set of strings
Set<String> s = new HashSet<String>();
s.add( "Geeks" );
s.add( "for" );
int n = s.size();
String arr[] = new String[n];
int i = 0 ;
for (String x : s)
arr[i++] = x;
System.out.println(Arrays.toString(arr));
}
} |
Output:
[Geeks, for]
Method 2 (Using System.arraycopy())
// Java program to demonstrate conversion of // Set to array using simple traversal import java.util.*;
class Test {
public static void main(String[] args)
{
// Creating a hash set of strings
Set<String> s = new HashSet<String>();
s.add( "Geeks" );
s.add( "for" );
int n = s.size();
String arr[] = new String[n];
// Copying contents of s to arr[]
System.arraycopy(s.toArray(), 0 , arr, 0 , n);
System.out.println(Arrays.toString(arr));
}
} |
Output:
[Geeks, for]
Method 3 (Using toArray())
// Java program to demonstrate conversion of // Set to array using toArray() import java.util.*;
class Test {
public static void main(String[] args)
{
// Creating a hash set of strings
Set<String> s = new HashSet<String>();
s.add( "Geeks" );
s.add( "for" );
int n = s.size();
String arr[] = new String[n];
// Please refer below post for syntax
// details of toArray()
arr = s.toArray(arr);
System.out.println(Arrays.toString(arr));
}
} |
Output:
[Geeks, for]
Method 4 (Using Arrays.copyOf())
// Java program to demonstrate conversion of // Set to array using Arrays.copyOf() import java.util.*;
class Test {
public static void main(String[] args)
{
// Creating a hash set of strings
Set<String> s = new HashSet<String>();
s.add( "Geeks" );
s.add( "for" );
String[] arr =
Arrays.copyOf(s.toArray(), s.size(), String[]. class );
System.out.println(Arrays.toString(arr));
}
} |
Output:
[Geeks, for]
Method 5 (Using stream in Java)
We use stream in Java to convert given set to steam, then stream to array. This works only in Java 8 or versions after that.
// Java program to demonstrate conversion of // Set to array using stream import java.util.*;
class Test {
public static void main(String[] args)
{
// Creating a hash set of strings
Set<String> s = new HashSet<String>();
s.add( "Geeks" );
s.add( "for" );
int n = s.size();
String[] arr = s.stream().toArray(String[] :: new );
System.out.println(Arrays.toString(arr));
}
} |
Output:
[Geeks, for]