# 
## What is an environment variable?

**Environment variable** is a dynamic value that the #key# OS: Operating System #key# and other applications may use to identify information particular to your machine.

The environment variables are in a *key-value* pair where the *key* indicates the variable’s name.

# 
#  Problem statement

Write a Java program to list all the environment variables with names and values.
# 
## Solution 

We use the `getenv()` static method of the `System` class in Java to retrieve all the environment variables.
##
## Syntax

``` java
public static java.util.Map<String, String> getenv()
```

The method takes no parameters. It returns a [Map](https://www.educative.io/answers/what-is-a-java-map) where the **map keys** are the environment variable name, and **map values** are the environment variable value.

# 
## Code

In the code below, we get all the environment in the form of `Map`. 

Next, we loop through the `Map` to get individual environment variable names and values.

import java.util.Map;

public class Main {

    public static void main(String[] args) {
        Map<String, String> envMap = System.getenv();

        for (String envName : envMap.keySet()) {
            System.out.format("%s = %s%n", envName, envMap.get(envName));
        }
    }
}

How to list all environment variables in Java

Use the `System.getenv()` method in Java to list all environment variables with their names and values.