Default values of primitives

In Java, fields (instance and static variables) are automatically initialized with default values if you don’t assign one. Local variables (inside methods) are not initialized automatically – you must assign a value before use.

Default values for primitive types

Type	Default value
`byte`	0
`short`	0
`int`	0
`long`	0L
`float`	0.0f
`double`	0.0d
`char`	`\u0000` (null character)
`boolean`	`false`

Example:

public class DefaultDemo {
    static int staticInt;        // default 0
    boolean boolField;           // default false
    char charField;              // default '\u0000'

    public static void main(String[] args) {
        int localInt;            // no default, must initialize
        // System.out.println(localInt); // compilation error
    }
}

For reference types (objects, arrays), the default value is null.

String str;   // default null

Important: Always initialize local variables before using them. The compiler enforces this.

public void method() {
    int x;
    if (condition) {
        x = 10;
    }
    // System.out.println(x); // error: variable might not have been initialized
}