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3.2.2 Reference Data Types (Strings, Objects)

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3.2.2 Reference Data Types (Strings, Objects)

While primitive data types store simple, direct values, Reference Data Types are a bit different. Imagine instead of putting the actual item in a box, you put a map or an address to where the item is stored in a much bigger warehouse.

Reference Data Types (often called "objects" in programming) don't store the actual data directly. Instead, they store a "reference" or a "memory address" that tells the computer where to find the actual data. The actual data (the object) is stored in a different, larger part of the computer's memory called the "heap."

Here are common reference data types:

  • Strings (Sequences of Characters/Text):
    • While a char holds a single letter, a String holds a whole sequence of characters, like a word, a sentence, or a paragraph.
    • Examples: "Hello World", "My name is Alex", "123 Main Street". (Notice they are usually put in double quotes).
    • Strings are incredibly common for storing names, addresses, messages, and any kind of text information.
    • In many languages (like Java), Strings are actually special kinds of objects, not primitive types.
  • Objects (Instances of Classes):
    • Remember Classes from Object-Oriented Programming? A class is like a blueprint. When you build something from that blueprint, you create an Object.
    • A reference data type variable for an object will hold the memory address of that specific object.
    • Examples:
      • If you have a Car blueprint (class), then myRedCar could be an object of type Car. The myRedCar variable would hold the address of where that specific red car's details (color, speed, etc.) are stored in memory.
      • A Dog object, a BankAccount object, a GameCharacter object.
    • These objects can be very complex, holding many pieces of data (properties) and having many actions they can perform (methods).

Key Difference from Primitive Types: When you copy a primitive type, you copy the value. When you copy a reference type, you copy the address. This means if two reference variables hold the same address, they are both pointing to and can change the same exact object.

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