How to Convert Stream to String in Java 8

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Introduction

In Java 8, the Stream API allows you to efficiently process collections and sequences of elements. Sometimes, after processing a stream, you might want to convert it into a String, either by joining the elements with a delimiter or concatenating them directly. Java 8 provides several ways to achieve this using the Collectors.joining() method.

This guide will demonstrate how to convert a stream to a string in Java 8.

Solution Steps

1. Create or Obtain a Stream: Generate or obtain a stream from a collection or another data source.
2. Use Collectors.joining(): Convert the stream into a string by joining the elements with or without a delimiter.
3. Display or Use the String: Print or use the resulting string.

Java Program

Example 1: Convert a Stream of Strings to a Single String (Without Delimiter)

import java.util.stream.Stream; import java.util.stream.Collectors; public class StreamToStringExample { public static void main(String[] args) { // Step 1: Create a stream of strings Stream<String> wordStream = Stream.of("Java", "is", "fun"); // Step 2: Convert the stream to a string without a delimiter String result = wordStream.collect(Collectors.joining()); // Step 3: Display the result System.out.println(result); // Output: "Javaisfun" } } 

Output

Javaisfun 

Explanation

• Step 1: A stream of strings is created using Stream.of().
• Step 2: The Collectors.joining() method is used to concatenate the elements without any delimiter.
• Step 3: The resulting string is printed.

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Example 2: Convert a Stream of Strings to a Single String (With a Space Delimiter)

import java.util.stream.Stream; import java.util.stream.Collectors; public class StreamToStringWithDelimiter { public static void main(String[] args) { // Step 1: Create a stream of strings Stream<String> wordStream = Stream.of("Java", "is", "fun"); // Step 2: Convert the stream to a string with a space delimiter String result = wordStream.collect(Collectors.joining(" ")); // Step 3: Display the result System.out.println(result); // Output: "Java is fun" } } 

Output

Java is fun 

Explanation

• Step 1: A stream of strings is created using Stream.of().
• Step 2: The Collectors.joining(" ") method is used to concatenate the elements with a space delimiter between them.
• Step 3: The resulting string is printed.

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Example 3: Convert a Stream of Integers to a String

import java.util.stream.Stream; import java.util.stream.Collectors; public class StreamOfIntegersToString { public static void main(String[] args) { // Step 1: Create a stream of integers Stream<Integer> numberStream = Stream.of(1, 2, 3, 4, 5); // Step 2: Convert the stream of integers to a string String result = numberStream.map(String::valueOf) .collect(Collectors.joining(", ")); // Step 3: Display the result System.out.println(result); // Output: "1, 2, 3, 4, 5" } } 

Output

1, 2, 3, 4, 5 

Explanation

• Step 1: A stream of integers is created using Stream.of().
• Step 2: The integers are converted to strings using map(String::valueOf) and then concatenated using Collectors.joining(", ").
• Step 3: The resulting string is printed.

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Example 4: Convert a Stream of Custom Objects to a String

import java.util.stream.Stream; import java.util.stream.Collectors; public class StreamOfObjectsToString { public static void main(String[] args) { // Step 1: Create a stream of Employee objects Stream<Employee> employeeStream = Stream.of( new Employee("Ravi", 30), new Employee("Amit", 25), new Employee("Pooja", 35) ); // Step 2: Convert the stream of Employee objects to a string String result = employeeStream.map(Employee::toString) .collect(Collectors.joining(", ")); // Step 3: Display the result System.out.println(result); } } class Employee { private String name; private int age; public Employee(String name, int age) { this.name = name; this.age = age; } @Override public String toString() { return name + ": " + age; } } 

Output

Ravi: 30, Amit: 25, Pooja: 35 

Explanation

• Step 1: A stream of Employee objects is created using Stream.of().
• Step 2: Each Employee object is converted to a string using map(Employee::toString) and then concatenated using Collectors.joining(", ").
• Step 3: The resulting string is printed.

Conclusion

In Java 8, converting a stream to a string is simple using the Collectors.joining() method. You can join the elements of the stream with or without a delimiter, and the process works for strings, numbers, or even custom objects. This approach is flexible and efficient for handling various data types.