What is Stream.sorted() method in Java?

Overview

The Stream.sorted() is the method of the Stream interface that returns a sorted stream. The elements of the stream are sorted according to their natural order or according to a provided Comparator. The sorted stream is new and does not affect the ordering of the elements in the original stream. This method is an intermediate operation and can be chained with other Stream operations.

Syntax

The syntax of the sorted() method is as follows:

stream.sorted()
Syntax of the sorted() method

Parameters

This method does not take any parameters.

Return value

This method returns a sorted stream.

Exceptions

This method may throw a ClassCastException, if the elements in the stream are not Comparable.

Code examples

The code example below shows how to use the sorted() method:

The sorted() method

Let's look at the code below:

import java.util.*; 
import java.util.stream.*; 
class StreamExample { 
    public static void main(String[] args) 
    { 
      Stream<Integer> stream = Stream.of(1, 3, 2, 6, 5, 8); 
      stream.sorted().forEach(System.out::println); 
    }
}

Code explanation

  • Line 7: We create a stream of integers.
  • Line 8: We invoke the sorted() method, which returns a sorted stream. The forEach() method prints each element of the sorted stream on a new line. It is an intermediate operation and does not affect the elements in the original stream.

The sorted() method with Comparator

We may use the sorted() method to sort the elements in reverse order by passing a Comparator as an argument. Let's look at the code below:

import java.util.*; 
import java.util.stream.*; 
class StreamExample { 
    public static void main(String[] args) 
    { 
      Stream<Integer> stream = Stream.of(1, 3, 2, 6, 5, 8); 
      stream.sorted((a, b)->b-a)
        .forEach(System.out::println);
    }
}

Code explanation

  • Line 7: We create a stream of integers.
  • Line 8: We call the sorted() method with a custom Comparator that sorts the elements in reverse order.

Sort objects of a user-defined class

We use the sorted() method to sort objects of a user-defined class by passing a Comparator as an argument. Let's look at the code below:

import java.util.*; 
import java.util.stream.*; 
 
class Employee { 
    int id, salary; 
    String name, designation; 
    // constructor 
    Employee(int id,String name,int salary,String designation) 
    {  
        this.id = id; 
        this.name = name; 
        this.salary = salary; 
        this.designation = designation; 
    }
    public String toString() {
      return "Employee{id=" + this.id 
      + ", name=\'" + this.name 
      + "\', salary=" + this.salary 
      + ", designation=\'" 
      + this.designation + "\'}"; 
    }
} 
class Example { 
  public static void main(String[] args) 
  {  
    List<Employee> list = new ArrayList<Employee>(); 
    // adding elements to the list 
    list.add(new Employee(1,"John",45000,"Manager")); 
    list.add(new Employee(2,"Martin",40000,"Developer"));  
    list.add(new Employee(3,"Sam",35000,"tester")); 
    // sorting the list according to the salary 
    // in ascending order 
    Stream<Employee> stream = list.stream(); 
    stream.sorted((e1, e2) -> e1.salary - e2.salary).forEach(System.out::println); 
  } 
}

Code explanation

  • Line 5: We create a Employee class with four fields: id, name, salary, and designation.
  • Lines 30 to 35: We create a list of Employee objects and add three elements to the list.
  • Line 39: We obtain a stream from the list using the stream() method.
  • Line 40: We call the sorted() method with a custom Comparator that compares two Employee objects by their salaries. Then, we use the forEach() method to print each element of the sorted stream on a new line.

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