Date: 6 Mar 2022

System Properties

Java system properties determine the environemnt in which the Java program run. Starting a Java Virtual Machine (JVM) sets the system properties for that instance of the JVM.

Java maintains a set of system properties for its operations. Each java system properties is a key-value (String-String) pair. For example, one such system properties is “java.vm.vendor:GraalVM Community”.

NOTE:

Please note that access to system properties can be restricted by the Java security manager and policy file. By default, Java programs have unrestricted access to all the system properties.

We can retrieve all the system properties via System.getProperties() or we can also retrieve individual property via System.getProperty(key) method.

In Java, we can use System.getProperties() to get all the system properties.

Properties properties = System.getProperties();
properties.forEach((k, v) -> System.out.println(k + ":" + v));

Example

SystemProperties.java

import java.util.Properties;

public class SystemProperties {
	public static void main(String[] args) {
		Properties properties = System.getProperties();
		properties.forEach((k, v) -> System.out.println(k + ":" + v));
	}
}

Sorted System Properties

SortedSystemProperties.java

import java.util.Properties;

public class SortedSystemProperties {
	public static void main(String[] args) {
		Properties properties = System.getProperties();

		LinkedHashMap<String, String> collect = properties.entrySet().stream()
			.collect(Collectors.toMap(k -> (String) k.getKey(), e -> (String) e.getValue())) 
			.entrySet().stream().sorted(Map.Entry.comparingByKey())
			.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, 
						(oldValue, newValue) -> oldValue, LinkedHashMap::new));

		collect.forEach((k, v) -> System.out.println(k + ":" + v));
	}
}