interface

Defines a contract — a set of method signatures that implementing classes must provide. Supports multiple inheritance.

Syntax

java

interface InterfaceName {
  returnType methodName(params);
}

Example

java

interface Drawable {
  void draw();
  default String getColor() { return "black"; }
}

class Circle implements Drawable {
  public void draw() { System.out.println("Drawing circle"); }
}