Properties class in Java
The properties object contains key and value pair both as a string. The java.util.Properties class is the subclass of Hashtable.
It can be used to get property value based on the property key. The Properties class provides methods to get data from properties file and store data into properties file. Moreover, it can be used to get properties of system.
Advantage of properties file
Recompilation is not required, if information is changed from properties file: If any information is changed from the properties file, you don't need to recompile the java class. It is used to store information which is to be changed frequently.
Methods of Properties class
The commonly used methods of Properties class are given below.
Example of Properties class to get information from properties file
To get information from the properties file, create the properties file first.db.properties
Now, lets create the java class to read the data from the properties file.Test.java
Now if you change the value of the properties file, you don't need to compile the java class again. That means no maintenance problem.
Example of Properties class to get all the system properties
By System.getProperties() method we can get all the properties of system. Let's create the class that gets information from the system properties.Test.java
Output: java.runtime.name = Java(TM) SE Runtime Environment sun.boot.library.path = C:\Program Files\Java\jdk1.7.0_01\jre\bin java.vm.version = 21.1-b02 java.vm.vendor = Oracle Corporation java.vendor.url = http://java.oracle.com/ path.separator = ; java.vm.name = Java HotSpot(TM) Client VM file.encoding.pkg = sun.io user.country = US user.script = sun.java.launcher = SUN_STANDARD ...........
Example of Properties class to create properties file
Now lets write the code to create the properties file.Test.java
Let's see the generated properties file.info.properties