this() function

[sung]

String book;
book.this()=book;

what does this() do here exactly?

thx guys

[mine0926]

I think its

 this.book = book

not

 book.this = book

Here is the explanation from its tutorial.
Using the this Keyword (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

[sung]

yeah sorry, made a mistake there :D

[sunde887]

In that situation it's to differentiate between the two items,
say you make the contructer that takes string book as an argument.

Book(String book){
  this.book = book;
}

says the object being created has a variable called book and you want to set it to the input book.

Book(String book){
  book = book;
}

this would not run correctly, if you used this constructor it wouldn't set the variable and you would create a null object.

Didn't notice the link to the tutorial above, that will definitely have the best information.

[m00nchile]

You can only use this() (or this(argtype arg) etc) inside a class. It is used for calling other constructors of your class:

public class MyClass {
  private int[] someArray;
  private String someString;
  public MyClass() {
    someArray = new int[10];
  }

  public MyClass(String arg) {
    this(); //calls the no arg constructor
    someString = arg;
  }
}

As already explained, this keyword is used as a reference an object keeps of itself, it's mainly used to differentiate inner scope variables with the objects variables that have the same name

public class MyClass {
  private String someString;
  public MyClass(String someString) {
    //someString = someString; this line sets the string passed to the constructor
    //to itself, doesn't make any sense
    this.someString = someString; //this line sets the objects someString variable 
    //to the string passed to the constructor
  }
}

[subith86]

I have put colors which mention which "book" comes where. See if you understand. The rest everything is as mentioned in the previous comments.

class Book {
	String [COLOR="Lime"][B]book[/B][/COLOR];
	Book(){}
	Book(String [B][COLOR="DeepSkyBlue"]book[/COLOR][/B]) {
		this.[COLOR="Lime"][B]book[/B][/COLOR] = [B][COLOR="DeepSkyBlue"]book[/COLOR][/B];
	}
}

[Fubarable]

subith, please ignore my last post which I've deleted. I see that you're answering the original question with color-coded code. Very cleverly done. Thanks.