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How to Print LinkedHashSet Elements in Java?
  • Last Updated : 28 Dec, 2020
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LinkedHashSet is a child class of HashSet in which duplicates are not allowed but the insertion order is preserved. The elements are printed in the same order in which they were inserted.

There are several ways to print LinkedHashSet elements:

  1. By simply printing the elements
  2. By using enhanced for loop
  3. Using iterator
  4. Using Arrays.toString()
  5. Printing elements of LinkedHashSet having objects of custom class using .toString() method of Object Class.

Method 1: Simply Printing the elements to console

  • We’ll first make an instance of the LinkedHashSet ,add the elements in it and simply print it to the console.
  • One method is to simply print the Collection object name and the contents of the LinkedHashSet will be printed.

Java




// Java program to print the elements of LinkedHashSet
  
import java.util.*;
class GfG {
    public static void main(String args[])
    {
  
        // Creating an instance of LinkedHashSet
        LinkedHashSet<String> hs = new LinkedHashSet<>();
  
        // Adding elements to the LinkedHashSet
        hs.add("Hey");
        hs.add("How");
        hs.add("are");
        hs.add("You");
  
        // Printing
        System.out.println(hs);
    }
}
Output
[Hey, How, are, You]

Method 2: Using Enchanced for loop 



We can simply print the elements using the enhanced for loop concept or for-each loop concept by iterating over all the LinkedHashSet elements.

To print the elements using for-each loop follow the following steps:-

  • Set up a for-each loop by declaring a variable of the same type as the base type of Collection class i.e. of the same type as the elements of LinkedHashSet, followed by a colon, which is then followed by the object name.
  • Inside the loop, simply print the variable name to display all the contents.

Java




// Java program to print the elements of LinkedHashSet
  
import java.util.*;
class GfG {
    public static void main(String[] args)
    {
        // Creating an instancce of LinkedHashSet
        LinkedHashSet<Integer> h = new LinkedHashSet<Integer>();
  
        // Adding elements to the LinkedHashSet
        h.add(1);
        h.add(5);
        h.add(3);
        h.add(9);
  
        // iterating and printing all the elements of
        // LinkedHashSet
        for (int i : h)
        {
            System.out.print(i + " ");
        }
    }
}
Output
1 5 3 9

Method 3: By using an Iterator

We can use an iterator over LinkedHashSet elements using the iterator method and print them using next() and hasNext() methods.

To cycle through the contents of the LinkedhashSet following steps will be followed:-

  • Obtain an iterator to start by calling an Iterator method.
  • Set up a loop that calls hasNext() and iterate until hasNext() return true.
  • Inside the loop, print each element using next().

Java




// Java program to print the elements of LinkedHashSet
  
import java.util.*;
  
class GfG {
    public static void main(String[] args)
    {
  
        // Creating an instance of LinkedHashSet
        LinkedHashSet<String> hnames = new LinkedHashSet<String>();
  
        // Adding elements to the LinkedHashSet
        hnames.add("Alok");
        hnames.add("Ayush");
        hnames.add("Abhinav");
        hnames.add("Akash");
        hnames.add("Atul");
  
        // Obtaining an Iterator
        Iterator<String> itr = hnames.iterator();
  
        // printing the elements in LinkedHashSet
        while (itr.hasNext())
        {
            System.out.println(itr.next());
        }
    }
}
Output
Alok
Ayush
Abhinav
Akash
Atul

Method 4: Using Array.toString()

To use it we first need to convert the LinkedHashSet to an array and then use the .toString() method to print them.

  • Convert the contents of the LinkedHashSet to an Array using .toArray method.
  • Now convert the arrays elements to their String representation using Arrays.toString() and print them.

Java




// Java program to print the elements of LinkedHashSet
  
import java.util.*;
  
class GfG {
    public static void main(String[] args)
    {
  
        // Creating an instance of LinkedHashSet
        LinkedHashSet<Integer> hnum
            = new LinkedHashSet<Integer>();
  
        // Adding elements to the LinkedHashSet
        hnum.add(678);
        hnum.add(789);
        hnum.add(876);
        hnum.add(589);
  
        // Converting the LinkedHashSet to Array
        // and then converting the array to string
        System.out.println(Arrays.toString(hnum.toArray()));
    }
}
Output
[678, 789, 876, 589]

Method 5: Printing elements of LinkedHashSet having objects of custom class

  • We can print the contents of the custom class simply by the below apporach but there is a key thing that needs to be kept in mind before printing it.
  • Whenever an object is printed its .toString() method  is called to get its String representation, if the custom class has not overridden the method then it is inherited from the Object class.
  • The toString() of the Object class prints the contents of the object as “ClassName@ObjectHashCode”, this would not be our requirement, so we override the toString() in the custom class so that only the information that we require will be printed.

Java




// Java program to print the elements of LinkedHashSet
  
import java.util.*;
class employee {
    private Integer salary;
    private String name;
  
    public employee(Integer salary, String name)
    {
        this.salary = salary;
        this.name = name;
    }
      
    // This method is of Object Class 
    // and whenever the object of employee 
    // class would be made then this method 
    // will be called by default 
    public String toString()
    {
        return "[" + this.name + "=>" + this.salary + "]";
    }
}
  
class GfG {
    public static void main(String[] args)
    {
  
        // Creating an instance of LinkedHashSet
        LinkedHashSet<employee> hemp = new LinkedHashSet<employee>();
  
        hemp.add(new employee(100000, "Ankush"));
        hemp.add(new employee(200000, "Atul"));
  
        System.out.println(hemp);
    }
}
Output
[[Ankush=>100000], [Atul=>200000]]

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