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A constructor in Java is a special method used to initialize objects. It is automatically invoked when an object is created using the new keyword. A constructor:
Has the same name as the class.
Does not have a return type (not even void).
Can be overloaded but not overridden.
1. Default Constructor A constructor with no parameters. If no constructor is defined, Java automatically provides one.
class Demo {Demo() {System.out.println("Default constructor");}public static void main(String[] args) {Demo obj = new Demo();}}コピーしました。✕コピーOutput: Default constructor
2. Parameterized Constructor Accepts parameters to initialize object properties.
class Demo {String name;int id;Demo(String name, int id) {this.name = name;this.id = id;}public static void main(String[] args) {Demo obj = new Demo("Alice", 101);System.out.println(obj.name + " - " + obj.id);}}コピーしました。✕コピーOutput: Alice - 101
3. Copy Constructor Initializes a new object by copying data from another object.
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