How do I print my Java object without getting SomeType 2f92e0f4

Question

I have a class defined as follows   public class Person     private String name        constructor and getter setter omitted     I tried to print an instance of my class   System out println myPerson     but I got the following output  com foo Person 2f92e0f4     A similar thing happened when I tried to print an array of Person objects   Person   people         System out println people      I got the output   Lcom foo Person  28a418fc  What does this output mean  How do I change this output so it contains the name of my person  And how do I print collections of my objects   Note  this is intended as a canonical Q amp A about this subject

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If you look at the Object class  Parent class of all classes in Java  the toString   method implementation is       public String toString            return getClass   getName           Integer toHexString hashCode             whenever you print any object in Java then toString   will be call  Now it s up to you if you override  toString   then your method will call other Object class method call

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I prefer to use a utility function which uses GSON to de-serialize the Java object into JSON string          This class provides basic common functionalities to be applied on Java Objects      public final class ObjectUtils        private static final Gson GSON   new GsonBuilder   setPrettyPrinting   create         private ObjectUtils              throw new UnsupportedOperationException  Instantiation of this class is not permitted in case you are using reflection                           This method is responsible for de-serializing the Java Object into Json String                 param object Object to be de-serialized          return String             public static String deserializeObjectToString final Object object            return GSON toJson object

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Background All Java objects have a toString   method  which is invoked when you try to print the object  System out println myObject       invokes myObject toString    This method is defined in the Object class  the superclass of all Java objects   The Object toString   method returns a fairly ugly looking string  composed of the name of the class  an   symbol and the hashcode of the object in hexadecimal  The code for this looks like     Code of Object toString   public String toString         return getClass   getName      quot   quot    Integer toHexString hashCode        A result such as com foo MyType 2f92e0f4 can therefore be explained as   com foo MyType  - the name of the class  i e  the class is MyType in the package com foo    - joins the string together 2f92e0f4 the hashcode of the object   The name of array classes look a little different  which is explained well in the Javadocs for Class getName    For instance   Ljava lang String means     - an single-dimensional array  as opposed to    or     etc   L - the array contains a class or interface java lang String - the type of objects in the array   Customizing the Output To print something different when you call System out println myObject   you must override the toString   method in your own class  Here s a simple example  public class Person      private String name          constructors and other methods omitted       Override   public String toString         return name         Now if we print a Person  we see their name rather than com foo Person 12345678  Bear in mind that toString   is just one way for an object to be converted to a string  Typically this output should fully describe your object in a clear and concise manner  A better toString   for our Person class might be   Override public String toString       return getClass   getSimpleName      quot  name  quot    name    quot   quot      Which would print  e g   Person name Henry   That s a really useful piece of data for debugging testing  If you want to focus on just one aspect of your object or include a lot of jazzy formatting  you might be better to define a separate method instead  e g  String toElegantReport           Auto-generating the Output Many IDEs offer support for auto-generating a toString   method  based on the fields in the class  See docs for Eclipse and IntelliJ  for example  Several popular Java libraries offer this feature as well  Some examples include   ToStringBuilder from Apache Commons Lang  MoreObjects ToStringHelper from Google Guava   ToString annotation from Project Lombok    Printing groups of objects So you ve created a nice toString   for your class  What happens if that class is placed into an array or a collection  Arrays If you have an array of objects  you can call Arrays toString   to produce a simple representation of the contents of the array  For instance  consider this array of Person objects  Person   people     new Person  quot Fred quot    new Person  quot Mike quot      System out println Arrays toString people        Prints   Fred  Mike   Note   this is a call to a static method called toString   in the Arrays class  which is different to what we ve been discussing above  If you have a multi-dimensional array  you can use Arrays deepToString   to achieve the same sort of output  Collections Most collections will produce a pretty output based on calling  toString   on every element  List lt Person gt  people   new ArrayList lt  gt     people add new Person  quot Alice quot     people add new Person  quot Bob quot         System out println people       Prints  Alice  Bob   So you just need to ensure your list elements define a nice toString   as discussed above

User · Answer

By default  every Object in Java has the toString   method which outputs the ObjectType HashCode    If you want more meaningfull information then you need to override the toString   method in your class    public class Person     private String name        constructor and getter setter omitted       overridding toString   to print name   public String toString         return name            Now when you print the person object using System out prtinln personObj   it will print the name of the person instead of the classname and hashcode    In your second case when you are trying to print the array  it prints  Lcom foo Person  28a418fc the Array type and it s hashcode      If you want to print the person names  there are many ways   You could write your own function that iterates each person and prints   void printPersonArray Person   persons       for Person person  persons           System out println person             You could print it using Arrays toString    This seems the simplest to me     System out println Arrays toString persons     System out println Arrays deepToString persons        for nested arrays     You could print it the java 8 way  using streams and method reference      Arrays stream persons  forEach System out  println     There might be other ways as well  Hope this helps

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I think apache provides a better util class which provides a function to get the string  ReflectionToStringBuilder toString object

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In Eclipse  Go to your class  Right click- source- Generate toString     It will override the toString   method and will print the object of that class

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In intellij you can auto generate toString method by  pressing alt inset and then selecting toString   here is an out put for a test class   public class test    int a  char b  String c  Test2 test2    Override public String toString         return  test                  a     a                  b     b                  c      c                         test2     test2                           As you can see  it generates a String by concatenating  several attributes of the class  for primitives it will print their values and for reference types it will use their class type  in this case to string method of Test2

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I managed to get this done using Jackson in Spring 5  Depending on the object Jackson might not work in all cases  import com fasterxml jackson databind ObjectMapper  import com fasterxml jackson databind SerializationFeature   ObjectMapper mapper   new ObjectMapper    Staff staff   createStaff       pretty print String json   mapper writerWithDefaultPrettyPrinter   writeValueAsString staff   System out println  quot ------------------------------------------------------------------- quot   System out println json   System out println  quot ------------------------------------------------------------------- quot    the output would be something like -------------------------------------------------------------------      quot id quot    1     quot internalStaffId quot     quot 1 quot      quot staffCms quot    1     quot createdAt quot     quot 1 quot      quot updatedAt quot     quot 1 quot      quot staffTypeChange quot    null     quot staffOccupationStatus quot    null     quot staffNote quot    null   -------------------------------------------------------------------  More examples using Jackson here You can try GSON also  Should be something like this  Gson gson   new Gson    System out println gson toJson objectYouWantToPrint  toString

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If you Directly print any object of Person It will the ClassName HashCode to the Code   in your case com foo Person 2f92e0f4 is getting printed   Where Person is a class to which object belongs and 2f92e0f4 is hashCode of the Object   public class Person     private String name     public Person String name     this name   name           getter setter omitted      override    public String toString            return name           Now if you try to Use the object of Person then it will print the name  Class Test      public static void main String    args       Person obj   new Person  YourName        System out println obj toString

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Every class in Java has the toString   method in it by default  which is called if you pass some object of that class to System out println    By default  this call returns the className hashcode of that object         SomeClass sc   new SomeClass           Class   followed by hashcode of object in Hexadecimal     System out println sc       You can override the toString method of a class to get different output  See this example  class A       String s    I am just a object        Override     public String toString                 return s           class B       public static void main String args                  A obj   new A            System out println obj

[java] How do I print my Java object without getting "SomeType@2f92e0f4"?

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