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Different name reusing techniques in Java

  • Difficulty Level : Easy
  • Last Updated : 05 Aug, 2021

Overriding An instance method overrides all accessible instance methods with the same signature in superclasses, enabling dynamic dispatch; in other words, the VM chooses which overriding to invoke based on an instance’s run-time type. Overriding is fundamental to object-oriented programming and is the only form of name reuse that is not generally discouraged:

Java




// Base Class
class Base {
public void f()
{ }
}
 
// Derived Class
class Derived extends Base {
 
// overrides Base.f()
public void f()
{ }
}

Hiding A field, static method, or member type hides all accessible fields, static methods, or member types, respectively, with the same name (or, for methods, signature) in supertypes. Hiding a member prevents it from being inherited : 

Java




// Base class
class Base {
   public static void f()
   { }
}
 
// Derived class
class Derived extends Base {
 
   // hides Base.f()
   public static void f()
   { }
}

Overloading Methods in a class overload one another if they have the same name and different signatures. The overloaded method designated by an invocation is selected at compile time: 

Java




// Base class
class GeeksForGeeks {
 
   // int overloading
   public void f(int i)
   { }
  
   // String overloading
   public void f(String s)
   { }
}

Shadowing A variable, method, or type shadows all variables, methods, or types, respectively, with the same name in a textually enclosing scope. If an entity is shadowed, you cannot refer to it by its simple name; depending on the entity, you cannot refer to it at all: 

Java




// Base class
class GeeksForGeeks {
 
static String sentence = "I don’t know.";
 
  public static void main(String[] args) {
 
     // shadows static field
     String sentence = "I know!";
 
     // prints local variable
     System.out.println(sentence);
  }
}

Although shadowing is generally discouraged, one common idiom does involve shadowing. Constructors often reuse a field name from their class as a parameter name to pass the value of the named field. This idiom is not without risk, but most Java programmers have decided that the stylistic benefits outweigh the risks:

Java




class Shirt {
   private final int size;
 
   // Parameter shadows Shirt.size
   public Shirt(int size) {
     this.size = size;
   }
}

Obscuring A variable obscures a type with the same name if both are in scope: If the name is used where variables and types are permitted, it refers to the variable. Similarly, a variable or a type can obscure a package. Obscuring is the only kind of name reuse where the two names are in different namespaces: variables, packages, methods, or types. If a type or a package is obscured, you cannot refer to it by its simple name except in a context where the syntax allows only a name from its namespace. Adhering to the naming conventions largely eliminates obscuring 

Java




public class Obscure {
 
  // Obscures type java.lang.System
  static String System;
 
  public static void main(String[] args) {
 
     // Next line won’t compile:
     // System refers to static field
     System.out.println("hello, obscure world!");
  }
}

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