What is the difference between canonical name, simple name and class name in Java Class?

Question

In Java, what is the difference between these:

Object o1 = ....
o1.getClass().getSimpleName();
o1.getClass().getName();
o1.getClass().getCanonicalName();
         


        

Answer 1

getName() – returns the name of the entity (class, interface, array class, primitive type, or void) represented by this Class object, as a String.

getCanonicalName() – returns the canonical name of the underlying class as defined by the Java Language Specification.

getSimpleName() – returns the simple name of the underlying class, that is the name it has been given in the source code.

package com.practice;

public class ClassName {
public static void main(String[] args) {

  ClassName c = new ClassName();
  Class cls = c.getClass();

  // returns the canonical name of the underlying class if it exists
  System.out.println("Class = " + cls.getCanonicalName());    //Class = com.practice.ClassName
  System.out.println("Class = " + cls.getName());             //Class = com.practice.ClassName
  System.out.println("Class = " + cls.getSimpleName());       //Class = ClassName
  System.out.println("Class = " + Map.Entry.class.getName());             // -> Class = java.util.Map$Entry
  System.out.println("Class = " + Map.Entry.class.getCanonicalName());    // -> Class = java.util.Map.Entry
  System.out.println("Class = " + Map.Entry.class.getSimpleName());       // -> Class = Entry 
  }
}

One difference is that if you use an anonymous class you can get a null value when trying to get the name of the class using the getCanonicalName()

Another fact is that getName() method behaves differently than the getCanonicalName() method for inner classes. getName() uses a dollar as the separator between the enclosing class canonical name and the inner class simple name.

To know more about retrieving a class name in Java.