1.6 Initializations

Learning Objectives

•Combine declaration and initialization in one statement.
•Explain the difference between default field initialization and required local-variable initialization.
•Initialize multiple variables of the same type in one statement.

Introduction

Initialization is giving a variable its first value, often combined with declaration in a single statement. Java treats declaration and initialization as separable steps for local variables, but requires initialization before first use — either explicitly by the programmer, or implicitly by the JVM for instance/class fields (which default to 0, false, or null).

Key Concepts

`int score = 0;` declares and initializes in a single statement.

Instance and class fields get automatic default values (0, 0.0, false, '\u0000', or null); local variables do not.

Multiple variables of the same type can be initialized together: `int x = 1, y = 2;`.

Java Syntax

Code Examples

`fieldCount` is a static field, so the JVM zero-initializes it automatically. `localCount` is a local variable inside `main`, so it must be assigned explicitly before use.

Common Mistakes

⚠Assuming local variables get a default value like fields do — they don't, and using one unassigned is a compile error.
⚠Splitting a multi-variable initializer incorrectly, e.g. `int x, y = 0;` only initializes `y`, not `x`.

Summary

Initialization gives a variable its first value. Fields get sensible defaults automatically; local variables must always be explicitly initialized before use.

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