Java · Theory

this Keyword in Java

Theory

32/270

this Keyword in Java

this means this current object. In a constructor, this.name = name; copies the parameter into the field. Without this, name = name; only changes the local parameter — a very common bug.

this.method() calls another method on the same object. this() calls another constructor in the same class and must be the first statement. static methods have no this, because there is no current object.

Show the classic constructor this.name = name; in interviews.

Let's take this on the board with one tiny Main class — no extra files. this Keyword in Java — output: Asha. Without this.name = name, the field would stay null — parameter would hide the field. Start from main, go line by line, and stop at each print. That output is the proof for this Keyword.

Exam tip

Show this.name = name in a constructor.

Example

class Person {
  String name;
  Person(String name) {
    this.name = name; // field = parameter
  }
}

public class Main {
  public static void main(String[] args) {
    Person p = new Person("Asha");
    System.out.println(p.name);
  }
}

this Keyword in Java — output: Asha. Without this.name = name, the field would stay null — parameter would hide the field.

Short notes

Defthis = this current object.
Rulethis.name = name; sets the field from the parameter.
Rememberthis() calls another constructor. Must be first statement.
TrapNo this in static methods. name = name; does not set the field.

Java · Theory

this Keyword in Java

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Theory

32/270

this Keyword in Java

this means this current object. In a constructor, this.name = name; copies the parameter into the field. Without this, name = name; only changes the local parameter — a very common bug.

Show the classic constructor this.name = name; in interviews.

Exam tip

Show this.name = name in a constructor.

Example

class Person {
  String name;
  Person(String name) {
    this.name = name; // field = parameter
  }
}

public class Main {
  public static void main(String[] args) {
    Person p = new Person("Asha");
    System.out.println(p.name);
  }
}

this Keyword in Java — output: Asha. Without this.name = name, the field would stay null — parameter would hide the field.

Short notes

Defthis = this current object.
Rulethis.name = name; sets the field from the parameter.
Rememberthis() calls another constructor. Must be first statement.
TrapNo this in static methods. name = name; does not set the field.

this Keyword in Java

Example

Short notes

Questions

this Keyword in Java

Example

Short notes

Questions