constuctor calling other constructor


I was reading as below

For one constructor to invoke another constructor, we use this keyword and pass
arguments within the parenthesis. Ex: this(10), this(10, ‘a’) etc.

I never remember calling one constructor from other constructor.
Which scenarios we need to call like above. what are practical uses of it. Please advise
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CPColinSenior Java ArchitectCommented:
Picture code like this:

public SomeClass
   public SomeClass()

   public SomeClass(int size)
      this(size, "a");

   public SomeClass(int size, String label)
      // Use the "size" and "label" values somehow.

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If you want to specify a specific value for the "size" and "label" parameters, you can call the constructor that takes two parameters. If you're okay with using the default value for "label", you can call the constructor that takes one parameter. If you're okay with using the default values for both "size" and "label", you can call the constructor that takes no parameters.

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We can find lots of places in Java's source code. Look at   
we can see line 185  
public Rectangle() {
    this(0, 0, 0, 0);

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and other examples in that code( line 196, 225, 239, 249, and 259).  
Look at API for details describing Rectangle class:
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