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Visibility control in java

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This document discusses visibility and access modifiers in Java. It describes the four access modifiers in Java - public, friendly/package, protected, and private. Public access makes a variable or method visible to all classes, friendly access limits visibility to the current package, protected access extends visibility to subclasses in the same and other packages, and private restricts visibility only to the class defining it. The document provides examples of when each access modifier would be used and summarizes their visibility scopes.

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VISIBILITY CONTROL IN JAVA
ACCESS MODIFIERS  Visibility modifiers also known as access modifiers can be applied to the instance variables and methods within a class.  Java provides the following access modifiers Public Friendly/Package (default) Private Protected
PUBLIC ACCESS  Any variable or method is visible to the entire class in which it is defined.  What is we want to make it visible to all classes outside the current class??  This is possible by simply declaring the variable as ‘public’ FRIENDLY ACCESS  When no access modifier member defaults to a limited version of public accessibility known as ‘friendly’ level of access. This is also known as package access.
 So what is the difference between the public and the friendly access???  The difference between the public and the friendly access is that public modifier makes the field visible in all classes regardless of their package while the friendly access make them visible only within the current package and not within the other packages.
PROTECTED ACCESS  The visibility level of the protected field lies between the private and the package access.  That is the protected access makes the field visible not only to all classes and subclasses in the same package but also to subclasses in other package  Non subclasses in their packages cannot access the protected members PRIVATE ACCESS  Enjoys high degree of protection.  They are accessible only within their own class  They cannot be inherited by their subclass and hence not visible in it.
Access Modifier Public Protected Friendly Private Access Location Same class Yes Yes Yes Yes Subclass in same package Yes Yes Yes No Other classes in same package Yes Yes Yes No Subclasses in other package Yes Yes No No Non subclasses in other package Yes No No No

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Visibility control in java

  • 2. ACCESS MODIFIERS  Visibility modifiers also known as access modifiers can be applied to the instance variables and methods within a class.  Java provides the following access modifiers Public Friendly/Package (default) Private Protected
  • 3. PUBLIC ACCESS  Any variable or method is visible to the entire class in which it is defined.  What is we want to make it visible to all classes outside the current class??  This is possible by simply declaring the variable as ‘public’ FRIENDLY ACCESS  When no access modifier member defaults to a limited version of public accessibility known as ‘friendly’ level of access. This is also known as package access.
  • 4. So what is the difference between the public and the friendly access???  The difference between the public and the friendly access is that public modifier makes the field visible in all classes regardless of their package while the friendly access make them visible only within the current package and not within the other packages.
  • 5. PROTECTED ACCESS  The visibility level of the protected field lies between the private and the package access.  That is the protected access makes the field visible not only to all classes and subclasses in the same package but also to subclasses in other package  Non subclasses in their packages cannot access the protected members PRIVATE ACCESS  Enjoys high degree of protection.  They are accessible only within their own class  They cannot be inherited by their subclass and hence not visible in it.
  • 6. Access Modifier Public Protected Friendly Private Access Location Same class Yes Yes Yes Yes Subclass in same package Yes Yes Yes No Other classes in same package Yes Yes Yes No Subclasses in other package Yes Yes No No Non subclasses in other package Yes No No No