Java Reference

Java references are the ways that variables refer to objects in Java. The term “reference” is often used to describe the way that variables of non-primitive types (i.e., object types) relate to the actual objects that they represent. A Java reference can be thought of as a way to access a particular object without necessarily knowing where that object resides in memory.

Here are a few key points to keep in mind:

1. Object Reference: In Java, all objects are dynamically allocated, which means they’re stored in a part of memory known as the heap. When you create an object, Java automatically assigns memory space for it in the heap. A reference to that object is returned, which you can assign to a variable. This variable doesn’t contain the object itself; rather, it contains a pointer or a reference to the object.

In this case, str is a reference to a new String object.

2. Null Reference: A null reference is one that doesn’t point to any object. In Java, null is a special value that indicates that a reference doesn’t point anywhere. Attempting to call methods on a null reference will result in a NullPointerException.

3. Reference Assignment: When you assign one reference variable to another, both will point to the same object. Changes made through one reference will be visible through the other.

4. Reference Types and Primitive Types: In Java, there are eight primitive types: boolean, byte, char, short, int, long, float, double. Every other type is a reference type, which includes classes, interfaces, arrays, and enums.