{"id":1194,"date":"2022-02-25T16:38:09","date_gmt":"2022-02-25T16:38:09","guid":{"rendered":"https:\/\/mdr.foobrdigital.com\/?p=1194"},"modified":"2022-02-25T16:38:09","modified_gmt":"2022-02-25T16:38:09","slug":"java-this-keyword","status":"publish","type":"post","link":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/2022\/02\/25\/java-this-keyword\/","title":{"rendered":"Java this Keyword"},"content":{"rendered":"\n

In this article, we will learn about this keyword in Java, how and where to use them with the help of examples.<\/p>\n\n\n\n

this Keyword<\/h2>\n\n\n\n

In Java, this keyword is used to refer to the current object inside a method or a constructor. For example,<\/p>\n\n\n\n

class Main {\n    int instVar;\n\n    Main(int instVar){\n        this.instVar = instVar;\n        System.out.println(\"this reference = \" + this);\n    }\n\n    public static void main(String[] args) {\n        Main obj = new Main(8);\n        System.out.println(\"object reference = \" + obj);\n    }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong>:<\/p>\n\n\n\n
this reference = Main@23fc625e\nobject reference = Main@23fc625e<\/samp><\/code><\/pre>\n\n\n\n
In the above example, we created an object named obj<\/var> of the class Main<\/var>. We then print the reference to the object obj<\/var> and this<\/code> keyword of the class.<\/p>\n\n\n\n
Here, we can see that the reference of both obj<\/var> and this<\/code> is the same. It means this is nothing but the reference to the current object.<\/p>\n\n\n\n
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Use of this Keyword<\/h2>\n\n\n\n
There are various situations where this<\/code> keyword is commonly used.<\/p>\n\n\n\n
Using this for Ambiguity Variable Names<\/h2>\n\n\n\n
In Java, it is not allowed to declare two or more variables having the same name inside a scope (class scope or method scope). However, instance variables and parameters may have the same name. For example,<\/p>\n\n\n\n
class MyClass {\n    \/\/ instance variable\n    int age;\n\n    \/\/ parameter\n    MyClass(int age){\n        age = age;\n    }\n}<\/code><\/pre>\n\n\n\n
In the above program, the instance variable and the parameter have the same name: age. Here, the Java compiler is confused due to name ambiguity.<\/p>\n\n\n\n
In such a situation, we use this keyword. For example,<\/p>\n\n\n\n
First, let’s see an example without using this<\/code> keyword:<\/p>\n\n\n\n
class Main {\n\n    int age;\n    Main(int age){\n        age = age;\n    }\n\n    public static void main(String[] args) {\n        Main obj = new Main(8);\n        System.out.println(\"obj.age = \" + obj.age);\n    }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong>:<\/p>\n\n\n\n
obj.age = 0<\/samp><\/code><\/pre>\n\n\n\n
In the above example, we have passed 8<\/code> as a value to the constructor. However, we are getting 0<\/code> as an output. This is because the Java compiler gets confused because of the ambiguity in names between instance the variable and the parameter.<\/p>\n\n\n\n
Now, let’s rewrite the above code using this<\/code> keyword.<\/p>\n\n\n\n
class Main {\n\n    int age;\n    Main(int age){\n        this.age = age;\n    }\n\n    public static void main(String[] args) {\n        Main obj = new Main(8);\n        System.out.println(\"obj.age = \" + obj.age);\n    }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong>:<\/p>\n\n\n\n
obj.age = 8<\/samp><\/code><\/pre>\n\n\n\n
Now, we are getting the expected output. It is because when the constructor is called, this<\/code> inside the constructor is replaced by the object obj<\/var> that has called the constructor. Hence the age<\/var> variable is assigned value 8<\/var>.<\/p>\n\n\n\n
Also, if the name of the parameter and instance variable is different, the compiler automatically appends this keyword. For example, the code:<\/p>\n\n\n\n
class Main {\n    int age;\n\n    Main(int i) {\n        age = i;\n    }\n}<\/code><\/pre>\n\n\n\n
is equivalent to:<\/p>\n\n\n\n
class Main {\n    int age;\n\n    Main(int i) {\n        this.age = i;\n    }\n}<\/code><\/pre>\n\n\n\n
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this with Getters and Setters<\/h3>\n\n\n\n
Another common use of this<\/code> keyword is in setters and getters methods<\/em> of a class. For example:<\/p>\n\n\n\n
class Main {\n   String name;\n\n   \/\/ setter method\n   void setName( String name ) {\n       this.name = name;\n   }\n\n   \/\/ getter method\n   String getName(){\n       return this.name;\n   }\n\n   public static void main( String[] args ) {\n       Main obj = new Main();\n\n       \/\/ calling the setter and the getter method\n       obj.setName(\"Toshiba\");\n       System.out.println(\"obj.name: \"+obj.getName());\n   }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong>:<\/p>\n\n\n\n
obj.name: Toshiba<\/samp><\/code><\/pre>\n\n\n\n
Here, we have used this<\/code> keyword:<\/p>\n\n\n\n