Crazy Java Handout P167 "6.2 Processing object 6.2.1 Print object and tostring method" slag residue note ctrl+c+v

 Example 2: 
1  Public classORC2 {3         Public Static classA4        {5                PublicString toString ()6               {7                      return"This is A";8               }9        }Ten         Public Static voidMain (string[] args) One        { AA obj =NewA (); - System.out.println (obj); -        } the}//output result!!

Example 2:

1  Public classORC2 {3         Public Static classA4        {5                PublicString getString ()6               {7                      return"This is A";8               }9        }Ten         Public Static voidMain (string[] args) One        { AA obj =NewA (); - System.out.println (obj); - System.out.println (obj.getstring ()); the        } -}

See the difference, theadvantage of ToString is that when encountering "println" such as the output method will be automatically called, do not explicitly hit out.

Introduction to a concept

1. Print object and ToString method: The ToString method is that the system will output the object's "self-describing" information to tell the external object that it has state information.

2. The ToString method provided by the object class always returns the class name + @ +hashcode value of the implementation class of the objects.

Two Print object examples

1. Program Example

1 class Person2 {3     PrivateString name;4      PublicPerson (String name)5     {6          This. Name =name;7     }8 }9  Public classPrintObjectTen { One      Public Static voidMain (string[] args) A     { -         //Create a Person object and assign it to the P variable -Person p =NewPerson ("Lin"); the         //Print the Person object referenced by P - System.out.println (p); -     } -}

2. Operation result

[Email protected]

3. Analysis of results

When you use this method to output a person object, the actual output is the ToString method of the Person object.

Three-Rewrite ToString Method Example

1. Program Example

1 classApple2 {3     PrivateString color;4     Private Doubleweight;5      PublicApple () {}6     //provides a constructor with parameters7      PublicApple (String color,Doubleweight)8     {9          This. color =color;Ten          This. Weight =weight; One     } A  -     //color Setter and Getter methods -      Public voidsetcolor (String color) the     { -          This. color =color; -     } -      PublicString GetColor () +     { -         return  This. Color; +     } A  at     //weight Setter and getter method -      Public voidSetweight (Doubleweight) -     { -          This. Weight =weight; -     } -      Public Doublegetweight () in     { -         return  This. Weight; to     } -     //override the ToString method to implement the "self-description" of an Apple object the      PublicString toString () *     { $         return"An apple, the color is:" +ColorPanax Notoginseng+ ", Weight is:" +weight; -     } the  + //Public String toString () A //    { the //return "apple[color=" + Color + ", weight=" + weight + "]"; + //    } -  $ } $  Public classtostringtest - { -      Public Static voidMain (string[] args) the     { -Apple A =NewApple ("Red", 2.38);Wuyi         //Print Apple Objects the System.out.println (a); -     } Wu}

2. Operation result

An apple, the color is: red, weight is: 2.38

3. Analysis of results

From the running results above, by overriding the Apple class's ToString method, you can have the system print out the "self-describing" information for an Apple object when it is printed.

Crazy Java Handout P167 "6.2 Processing object 6.2.1 Print object and tostring method" slag residue note ctrl+c+v