CODEWITHSUNDEEP
java
user297850
user297850

Reputation: 8015

the usage of this in the class definition

With respect to the following class definition:

public final class ConfigComparer {
    ...some code ....

    public ConfigComparer(String defaultFile, String siteFile)
       throws NoSuchFieldException, IllegalAccessException {
       this.defaultFile = defaultFile;
       this.siteFile = siteFile;
       defaultConfig = loadConfiguration(defaultFile);
       siteConfig = loadConfiguration(siteFile);
       load();
    }
    ..... some code  ....

}

Inside the constructor ConfigComparer, there are this.defaultFile = defaultFile; and this.siteFile = siteFile; what are these two this. used for or what are their design considerations?

Upvotes: 2

Views: 68

Answers (4)

Omar Mainegra
Omar Mainegra

Reputation: 4194

The class definition should be something like this:

public final class ConfigComparer {

    private String defaultFile;

    private String siteFile;

    ...some code ....
}

And, in the constructor, you are assigning the parameters (String defaultFile, String siteFile) to those attributes. Note that if the attributes would have a different name this is not required, but in this case it it, if not then you are assigning to the parameters their same value.

Upvotes: 0

Sajan Chandran
Sajan Chandran

Reputation: 11487

As per the link, this refers to Within an instance method or a constructor, this is a reference to the current object

Your code constructor can be written without this keyword like

public ConfigComparer(String defaultFile, String siteFile)
   throws NoSuchFieldException, IllegalAccessException {
   instance_defaultFile = defaultFile;
   instance_siteFile = siteFile;
   defaultConfig = loadConfiguration(defaultFile);
   siteConfig = loadConfiguration(siteFile);
   load();
}

In your constructor, the keyword this is necessary since both your instance variable and your method parameter are the same, the jvm needs to know what you are referring to and thats why you need to say

this.defaultFile = defaultFile

Upvotes: 0

Cruncher
Cruncher

Reputation: 7796

this refers to the instance/object that your code is running inside.

this.defaultFile references the instance variable defaultFile of the class ConfigComparer.

defaultFile references the variable passed into the constructor.

When this is not specified, it always looks for local variables, before instance variables.

Upvotes: 3

Jayaram
Jayaram

Reputation: 1725

Within an instance method or a constructor, this is a reference to the current object — the object whose method or constructor is being called. You can refer to any member of the current object from within an instance method or a constructor by using this.

From within a constructor, this keyword to call another constructor in the same class. Doing so is called an explicit constructor invocation.

Source: http://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html

Upvotes: 0

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