Convert a Map to a String in Java

This post will discuss how to convert a Map to a String in Java.

1. Using `toString()` method

A simple approach is to get the string representation of the map using the toString() method. The string representation of a map consists of a list of key-value pairs enclosed within curly braces, where the adjacent pairs are delimited by a comma followed by a single space and each key-value pair is separated by the equals sign (=). i.e., {K₁=V₁, K₂=V₂, ..., K_n=V_n}.

Following is a simple example demonstrating the string representation of the map:

import java.util.HashMap;

import java.util.Map;

public class Main

{

public static void main(String[] args)

{

Map<String, Integer> lang = new HashMap<>();

lang.put("C++", 1980);

lang.put("Java", 1995);

lang.put("Ruby", 1991);

String str = lang.toString();

System.out.println(str);

}

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Output:

{Java=1995, C++=1980, Ruby=1991}

2. Using Guava

Guava’s Joiner class is designed to customize the string representation of an object. Just create a joiner, and configure the separator, and specify the collection to be added.

The following code demonstrates it:

import com.google.common.base.Joiner;

import java.util.HashMap;

import java.util.Map;

public class Main

{

public static void main(String[] args)

{

Map<String, Integer> lang = new HashMap<>();

lang.put("C++", 1980);

lang.put("Java", 1995);

lang.put("Ruby", 1991);

String str = Joiner.on("|").withKeyValueSeparator(":").join(lang);

System.out.println(str);

}

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Output:

Java:1995|C++:1980|Ruby:1991

3. Using Stream API

With Java 8 and above, you can get the string representation of a map using a Stream API, easily customized according to your needs.

import java.util.HashMap;

import java.util.Map;

import java.util.stream.Collectors;

public class Main

{

public static void main(String[] args)

{

Map<String, Integer> lang = new HashMap<>();

lang.put("C++", 1980);

lang.put("Java", 1995);

lang.put("Ruby", 1991);

String str = lang.entrySet().stream().map(e -> e.getKey() + ":" + e.getValue())

.collect(Collectors.joining("|"));

System.out.println(str);

}

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Output:

Java:1995|C++:1980|Ruby:1991

That’s all about converting a Map to a String in Java.

Convert a Map to a String in Java

1. Using toString() method

2. Using Guava

3. Using Stream API

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1. Using `toString()` method