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viana
Asked: 2020-10-04 21:29:33 +0800 CST 2020-10-04 21:29:33 +0800 CST

What difference between getCanonicalName() and getName() methods?

  • 772

To return the package name with the class name in Java I have always used the getName(). I noticed that apparently the method getCanonicalName()returns the same thing.

See just an example customizing the method toString():

@Override
public String toString() {
    return this.getClass().getName();
}

Isso would apparently be equivalent to:

@Override
public String toString() {
    return this.getClass().getCanonicalName();
}

What is the actual difference between the getCanonicalName()and methods getName()?

java

2 Answers

  1. Best Answer

    getName() Returns the name of the entity (class, interface, array, primitive type, or void) represented by this class object, as a string. This name is used to dynamically load the class using Class.forName()

    getCanonicalName() Returns the canonical name of the underlying class defined by the Java language specification. Returns null if the underlying class does not have a canonical name (that is, if it is a local or anonymous class or an array whose component type does not have a canonical name). This is the name that would be used in an import statement and would uniquely identify the class. It can be useful during logging operations.

    package com.myapp;

import java.lang.*;

public class ClaseDemo {

   public static void main(String[] args) {

    ClaseDemo c = new ClaseDemo();
    Class clase = c.getClass();    
    System.out.println("Clase: " + clase.getCanonicalName()); 

   }
}

    Gets as output:

    Clase: com.myapp.ClaseDemo

    I think it is important to also add:

    getSimpleName() Returns the "simple name" of the underlying class as indicated in the source code. Returns an empty string if the underlying class is anonymous. Loosely identifies the class, may be useful during logging operations, but is not guaranteed to be unique.

    package com.myapp;

import java.lang.*;

public class ClaseDemo {

   public static void main(String[] args) {

    ClaseDemo c = new ClaseDemo();
    Class clase = c.getClass();    
    System.out.println("Clase: " + clase.getSimpleName()); 

   }
}

    Gets as output:

    Clase: ClaseDemo

    An important difference is that if you use an anonymous class you can get a null value when trying to get the class name usinggetCanonicalName()

    getName() 

    Clase: com.myapp.ClaseDemo

    getCanonicalName() 

    Clase: null

    getSimpleName() 

    Clase: ClaseDemo
    • 4

  2. I will explain it to you with a test:

    //primitive
System.out.println(int.class.getName());
System.out.println(int.class.getCanonicalName());

System.out.println();

//class
System.out.println(String.class.getName());
System.out.println(String.class.getCanonicalName());

System.out.println();

//inner class
System.out.println(HashMap.SimpleEntry.class.getName());
System.out.println(HashMap.SimpleEntry.class.getCanonicalName());   

System.out.println();

//anonymous inner class
System.out.println(new Serializable(){}.getClass().getName());
System.out.println(new Serializable(){}.getClass().getCanonicalName());

    Result:

    int
int

java.lang.String
java.lang.String

java.util.AbstractMap$SimpleEntry
java.util.AbstractMap.SimpleEntry

ClassnameTest$1
null

    The result of looking at this is:

    The name is the name you would use to dynamically load the class with, for example, a call to Class.forNamewith ClassLoaderdefault.

    The canonical name is the name that would be used in an import statement and would uniquely identify the class. It can be useful during toStringlog operations.

    • 3