The basics of Collection in Java

Collection, this may be another most advanced section in Java. I think you may hear that there are so many things to learn about Collections. Let's begin our journey.

What is the Collection & Collection framework?

• The collection is just a collection of objects or data.
• The Java collection framework is an architecture that is used to manage collections in Java.
• The Java Collection framework consists of interfaces, implementations and also algorithms.

Core collection interface hierarchy

As you can see, Map is a separate collection interface. Because it stores values with a key.

Advanced collection hierarchy

Click on image for clear view

Click on image for clear view

How to select which Collection is needed?

Collection hierarchy is a big one, but you can identify it easily. Look at the following diagram. Begin with the blue color checking statement.

Click on image for clear view

Collection vs Collections

• The collection is an interface and it is the root interface of the Java Collection framework.
• Collections is a utility class which is from java.util package.
• Collections class consists of core methods that can be used commonly with List, Set and Queue. 
• There are so many methods that are defined in the Collections class.

List vs Set vs Queue vs Map

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Advantages of using the Collection framework 

• No need to learn new APIs or create new APIs.
• Increase speed and interoperability.
• Reduce programming effort.
• It increases software reuse.