Java Properties Class

Introduction

The Java Properties class is a class which represents a persistent set of properties. The Properties can be saved to a stream or loaded from a stream. Following are the important points about Properties −

• Each key and its corresponding value in the property list is a string.

• A property list can contain another property list as its 'defaults', this second property list is searched if the property key is not found in the original property list.

• This class is thread-safe; multiple threads can share a single Properties object without the need for external synchronization.

Class declaration

Following is the declaration for java.util.Properties class −

public class Properties
   extends Hashtable<Object,Object>

Field

Following are the fields for java.util.Properties class −

protected Properties defaults − This is the property list that contains default values for any keys not found in this property list.

Class constructors

Class methods

Methods inherited

This class inherits methods from the following classes −

• java.util.Hashtable
• java.util.Object

Getting an Enumeration of Properties Keys Example

The following example shows the usage of java.util.Properties.propertyNames() method.

package com.tutorialspoint;

import java.util.Enumeration;
import java.util.Properties;

public class PropertiesDemo {
   public static void main(String[] args) {
      Properties prop = new Properties();

      // add some properties
      prop.put("Height", "200");
      prop.put("Width", "15");

      // assign the property names in a enumaration
      Enumeration<?> enumeration = prop.propertyNames();

      // print the enumaration elements
      while(enumeration.hasMoreElements()) {
         System.out.println("" + enumeration.nextElement());  
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Width
Height