How to override toString properly in Java

Question

Sounds a little stupid  but I need help on my toString   method and it is very irking   I tried looking up online because the toString is the one where it is screwing up and  not finding Kid constructor  2  even though it is there and I would even do something else and it doesn t work  Ok that was a lot so here is my code    import java util        class Kid           String name         double height         GregorianCalendar bDay          public Kid                this name    HEAD            this height   1            this bDay   new GregorianCalendar 1111 1 1                    public Kid  String n  double h  String date             method that toString   can t find somehow          StringTokenizer st   new StringTokenizer date       true            n   this name           h   this height                  public String toString               return Kid this name  this height  this bDay                   end class    Ok So my toString above  I know  my third parameter is off  should be a String  is off  If I hardcode a value in for the third thing it goes haywire and says it can t find this  up above   So how can I get the date and break it up   Class calling this is below  class Driver         public static void main  String   args             Kid kid1   new Kid  Lexie   2 6   11 5 2009             System out println kid1 toString            end main method      end class     I tried researching multiple constructors and it really didn t help  I tried researching toString   methods  and tried using previous toString   methods logic that I created previous but this is brand new so it never worked   Help

User · Answer

The best way in my opinion is using google gson library:

        @Override
public String toString() {
    return new GsonBuilder().setPrettyPrinting().create().toJson(this);
}

or apache commons lang reflection way

User · Answer

Always have easy way  Right Click  gt  Generate  gt  toString    gt  select template that you want

User · Answer

Following code is a sample  Question based on the same  instead of using IDE based conversion  is there a faster way to implement so that in future the changes occur  we do not need to modify the values over and over again    Override     public String toString             return  ContractDTO                      contractId      contractId                             contractTemplateId      contractTemplateId

User · Answer

You can creating new object in the toString    use  return  Name       this name    height      this height    instead of   return Kid this name  this height  this bDay     You may change the return string as required  There are other ways to store date instead calander

User · Answer

The toString is supposed to return a String   public String toString          return  Name       this name       Height       this height       Birthday       this bDay             I suggest you make use of your IDE s features to generate the toString method  Don t hand-code it   For instance  Eclipse can do so if you simply right-click on the source code and select Source  gt  Generate toString

User · Answer

Well actually you will need to return something like this because toString has to return a string  public String toString      return  Name      this name    whatever      this whatever           and you actually do something wrong in the constructer you set the variable the user set to the name while you need to do the opposite  What you shouldn t do  n   this name   What you should do  this name   n   Hopes this helps thanks

User · Answer

You can t call a constructor as if it was a normal method  you can only call it with new to create a new object   Kid newKid   new Kid this name  this height  this bDay     But constructing a new object from your toString   method is not what you want to be doing

User · Answer

if you are use using notepad  then      public String toString      return     ---now here you can use variables which you have created for your class     if you are using eclipse IDE then press  -alt  shift  s    -click on override toString method here you will get options to select what type of variables you want to select

User · Answer

If you re interested in Unit-Tests  then you can declare a public  ToStringTemplate   and then you can unit test your toString   Even if you don t unit-test it  I think its  cleaner  and uses String format   public class Kid        public static final String ToStringTemplate    KidName   1s   Height   2s   GregCalendar   3s         private String kidName      private double height      private GregorianCalendar gregCalendar       public String getKidName             return kidName             public void setKidName String kidName            this kidName   kidName             public double getHeight             return height             public void setHeight double height            this height   height             public GregorianCalendar getGregCalendar             return gregCalendar             public void setGregCalendar GregorianCalendar gregCalendar            this gregCalendar   gregCalendar             public String toString              return String format ToStringTemplate  this getKidName    this getHeight    this getGregCalendar                Now you can unit test by create the Kid  setting the properties  and doing your own string format on the ToStringTemplate and comparing   making ToStringTemplate static-final means  ONE VERSION  of the truth  rather than having a  copy  of the template in the unit-test

User · Answer

Java toString   method  If you want to represent any object as a string  toString   method comes into existence   The toString   method returns the string representation of the object   If you print any object  java compiler internally invokes the toString   method on the object  So overriding the toString   method  returns the desired output  it can be the state of an object etc  depends on your implementation   Advantage of Java toString   method  By overriding the toString   method of the Object class  we can return values of the object  so we don t need to write much code   Output without toString   method  class Student     int id     String name     String address      Student int id  String name  String address      this id id     this name name     this address address           public static void main String args          Student s1 new Student 100    Joe       success           Student s2 new Student 50    Jeff       fail            System out println s1    compiler writes here s1 toString        System out println s2    compiler writes here s2 toString               Output Student 2kaa9dc        Student 4bbc148   You can see in the above example  1   printing s1 and s2 prints the Hashcode values of the objects but I want to print the values of these objects  Since java compiler internally calls toString   method  overriding this method will return the specified values  Let s understand it with the example given below   Example 2  Output with overriding toString   method  class Student     int id     String name     String address      Student int id  String name  String address      this id id     this name name     this address address            overriding the toString   method   public String toString       return id     name     address          public static void main String args          Student s1 new Student 100    Joe       success           Student s2 new Student 50    Jeff       fail            System out println s1    compiler writes here s1 toString        System out println s2    compiler writes here s2 toString              Output 100 Joe success        50 Jeff fail   Note that toString   mostly is related to the concept of polymorphism in Java  In  Eclipse  try to click on toString   and right click on it Then  click on Open Declaration and see where the Superclass toString   comes from

User · Answer

Nice and concise way is to use Lombok annotations  It has  ToString annotation  which will generate an implementation of the toString   method  By default  it will print your class name  along with each field  in order  separated by commas  You can easily customize your output by passing parameters to annotation  e g     ToString of     name    lastName      Which is equivalent of pure Java   public String toString             return  Person name     this name      lastName     this experienceInYears

User · Answer

we can even write like this by creating a new String object in the class and assigning it what ever we want in constructor and return that in toString method which is overridden  public class Student     int id     String name     String address     String details   Student int id  String name  String address      this id id     this name name     this address address     this details id      name      address            overriding the toString   method   public String toString       return details          public static void main String args          Student s1 new Student 100  Joe   success         Student s2 new Student 50  Jeff   fail          System out println s1    compiler writes here s1 toString        System out println s2    compiler writes here s2 toString

User · Answer

If you re just using toString   for debugging a DTO  you can generate human readable output automatically with something like the following     import com fasterxml jackson databind ObjectMapper      public String toString         try   return new ObjectMapper   writeValueAsString this         catch  Exception e    return   ObjectMapper failed            However  this isn t appropriate for production deployments if the DTO may contain PII  which shouldn t be captured in logs

User · Answer

As others explained  the toString is not the place to be instantiating your class  Instead  the toString method is intended to build a string representing the value of an instance of your class  reporting on at least the most important fields of data stored in that object  In most cases  toString is used for debugging and logging  not for your business logic     To generate text representing the value of an object for display to a user  add another method  People often name the method something like getDisplayName  For example  DayOfWeek  getDisplayName and Month  getDisplayName   StringJoiner  As of Java 8 and later  the most modern way to implement toString would use the StringJoiner class  As the doc says      StringJoiner is used to construct a sequence of characters separated by a delimiter and optionally starting with a supplied prefix and ending with a supplied suffix    Use like this    Override public String toString          return new StringJoiner                               In Java 8 and later  StringJoiner is used to construct a sequence of characters separated by a delimiter and optionally starting with a supplied prefix and ending with a supplied suffix                                                            Delimiter                 Person class getSimpleName                Prefix                                                           Suffix                            add   name     name                          Append              add   phone     phone                        Append              toString                                     Convert entire sequence to a single  String  object         Person  name Alice   phone 555 867 5309

[java] How to override toString() properly in Java?

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