How to prevent changing the value of variable?












7















I am a beginner in java. When developing a program, I created an object with a constructor with variables as arguments. But when I change the value of the variable after creating the object, my object has the second value instead of the first one. I don't want my object to change the value. What do I do?



public class Person {

public Person(int arrayTest) {
this.arrayTest = arrayTest;
}
public int getArray() {
return this.arrayTest;
}
public boolean canHaveAsArray(int arrayTest) {
return true;
}
private int arrayTest = new int[2];

public static void main(String args) {
int array = new int {5, 10};
Person obj1 = new Person(array);
array[0] = 20;
System.out.println(Arrays.toString(obj1.getArray()));
}
}


My output should be [5, 10], but instead, I am getting [20,10]. I need to get [5,10] even when I change an element of the array as shown above. What should I do?










share|improve this question



























    7















    I am a beginner in java. When developing a program, I created an object with a constructor with variables as arguments. But when I change the value of the variable after creating the object, my object has the second value instead of the first one. I don't want my object to change the value. What do I do?



    public class Person {

    public Person(int arrayTest) {
    this.arrayTest = arrayTest;
    }
    public int getArray() {
    return this.arrayTest;
    }
    public boolean canHaveAsArray(int arrayTest) {
    return true;
    }
    private int arrayTest = new int[2];

    public static void main(String args) {
    int array = new int {5, 10};
    Person obj1 = new Person(array);
    array[0] = 20;
    System.out.println(Arrays.toString(obj1.getArray()));
    }
    }


    My output should be [5, 10], but instead, I am getting [20,10]. I need to get [5,10] even when I change an element of the array as shown above. What should I do?










    share|improve this question

























      7












      7








      7








      I am a beginner in java. When developing a program, I created an object with a constructor with variables as arguments. But when I change the value of the variable after creating the object, my object has the second value instead of the first one. I don't want my object to change the value. What do I do?



      public class Person {

      public Person(int arrayTest) {
      this.arrayTest = arrayTest;
      }
      public int getArray() {
      return this.arrayTest;
      }
      public boolean canHaveAsArray(int arrayTest) {
      return true;
      }
      private int arrayTest = new int[2];

      public static void main(String args) {
      int array = new int {5, 10};
      Person obj1 = new Person(array);
      array[0] = 20;
      System.out.println(Arrays.toString(obj1.getArray()));
      }
      }


      My output should be [5, 10], but instead, I am getting [20,10]. I need to get [5,10] even when I change an element of the array as shown above. What should I do?










      share|improve this question














      I am a beginner in java. When developing a program, I created an object with a constructor with variables as arguments. But when I change the value of the variable after creating the object, my object has the second value instead of the first one. I don't want my object to change the value. What do I do?



      public class Person {

      public Person(int arrayTest) {
      this.arrayTest = arrayTest;
      }
      public int getArray() {
      return this.arrayTest;
      }
      public boolean canHaveAsArray(int arrayTest) {
      return true;
      }
      private int arrayTest = new int[2];

      public static void main(String args) {
      int array = new int {5, 10};
      Person obj1 = new Person(array);
      array[0] = 20;
      System.out.println(Arrays.toString(obj1.getArray()));
      }
      }


      My output should be [5, 10], but instead, I am getting [20,10]. I need to get [5,10] even when I change an element of the array as shown above. What should I do?







      java






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 1 hour ago









      OpheliaOphelia

      362




      362
























          2 Answers
          2






          active

          oldest

          votes


















          5














          Array is passed by reference in Java. If you pass the original array to the constructor of Person, you are just passing the reference to the original array and the changes in original array will reflect in Person instance.



          So if you don't want to change the value of array in Person so don't pass the original array, instead just send a copy of original array like below:



          Person obj1 = new Person(java.util.Arrays.copyOf(array, array.length));


          You can also modify the code in Person constructor to achieve the same results:



          public Person(int arrayTest) {
          this.arrayTest = java.util.Arrays.copyOf(arrayTest, arrayTest.length);
          }





          share|improve this answer

































            3














            There is no such thing as immutable (unchangeable) array in Java. The Java language does not support this, and neither does the JVM. You can't solve this at the language level.



            In general, the only way to prevent changes to an array is to not share the reference to the array with other code that might change it.



            In your example, you have what is known as a leaky abstraction. You are passing an array to your Person class, and the caller is keeping a reference to that array so that it can change it. To solve this, you can:




            • copy the array, and pass a reference to the copy, or

            • have the constructor (or a setter for the array attribute) make the copy.


            (See answer https://stackoverflow.com/a/55428214/139985 for example code.)



            The second alternative is preferable from an OO perspective. The Person class should be responsible for preserving its own internal state from interference ... if that is your design requirement. It should not rely on the caller to do this. (Even if the caller is technically part of the same class as is the case here.)






            share|improve this answer


























              Your Answer






              StackExchange.ifUsing("editor", function () {
              StackExchange.using("externalEditor", function () {
              StackExchange.using("snippets", function () {
              StackExchange.snippets.init();
              });
              });
              }, "code-snippets");

              StackExchange.ready(function() {
              var channelOptions = {
              tags: "".split(" "),
              id: "1"
              };
              initTagRenderer("".split(" "), "".split(" "), channelOptions);

              StackExchange.using("externalEditor", function() {
              // Have to fire editor after snippets, if snippets enabled
              if (StackExchange.settings.snippets.snippetsEnabled) {
              StackExchange.using("snippets", function() {
              createEditor();
              });
              }
              else {
              createEditor();
              }
              });

              function createEditor() {
              StackExchange.prepareEditor({
              heartbeatType: 'answer',
              autoActivateHeartbeat: false,
              convertImagesToLinks: true,
              noModals: true,
              showLowRepImageUploadWarning: true,
              reputationToPostImages: 10,
              bindNavPrevention: true,
              postfix: "",
              imageUploader: {
              brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
              contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
              allowUrls: true
              },
              onDemand: true,
              discardSelector: ".discard-answer"
              ,immediatelyShowMarkdownHelp:true
              });


              }
              });














              draft saved

              draft discarded


















              StackExchange.ready(
              function () {
              StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55428172%2fhow-to-prevent-changing-the-value-of-variable%23new-answer', 'question_page');
              }
              );

              Post as a guest















              Required, but never shown

























              2 Answers
              2






              active

              oldest

              votes








              2 Answers
              2






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              5














              Array is passed by reference in Java. If you pass the original array to the constructor of Person, you are just passing the reference to the original array and the changes in original array will reflect in Person instance.



              So if you don't want to change the value of array in Person so don't pass the original array, instead just send a copy of original array like below:



              Person obj1 = new Person(java.util.Arrays.copyOf(array, array.length));


              You can also modify the code in Person constructor to achieve the same results:



              public Person(int arrayTest) {
              this.arrayTest = java.util.Arrays.copyOf(arrayTest, arrayTest.length);
              }





              share|improve this answer






























                5














                Array is passed by reference in Java. If you pass the original array to the constructor of Person, you are just passing the reference to the original array and the changes in original array will reflect in Person instance.



                So if you don't want to change the value of array in Person so don't pass the original array, instead just send a copy of original array like below:



                Person obj1 = new Person(java.util.Arrays.copyOf(array, array.length));


                You can also modify the code in Person constructor to achieve the same results:



                public Person(int arrayTest) {
                this.arrayTest = java.util.Arrays.copyOf(arrayTest, arrayTest.length);
                }





                share|improve this answer




























                  5












                  5








                  5







                  Array is passed by reference in Java. If you pass the original array to the constructor of Person, you are just passing the reference to the original array and the changes in original array will reflect in Person instance.



                  So if you don't want to change the value of array in Person so don't pass the original array, instead just send a copy of original array like below:



                  Person obj1 = new Person(java.util.Arrays.copyOf(array, array.length));


                  You can also modify the code in Person constructor to achieve the same results:



                  public Person(int arrayTest) {
                  this.arrayTest = java.util.Arrays.copyOf(arrayTest, arrayTest.length);
                  }





                  share|improve this answer















                  Array is passed by reference in Java. If you pass the original array to the constructor of Person, you are just passing the reference to the original array and the changes in original array will reflect in Person instance.



                  So if you don't want to change the value of array in Person so don't pass the original array, instead just send a copy of original array like below:



                  Person obj1 = new Person(java.util.Arrays.copyOf(array, array.length));


                  You can also modify the code in Person constructor to achieve the same results:



                  public Person(int arrayTest) {
                  this.arrayTest = java.util.Arrays.copyOf(arrayTest, arrayTest.length);
                  }






                  share|improve this answer














                  share|improve this answer



                  share|improve this answer








                  edited 1 hour ago

























                  answered 1 hour ago









                  Aniket SahrawatAniket Sahrawat

                  6,32121339




                  6,32121339

























                      3














                      There is no such thing as immutable (unchangeable) array in Java. The Java language does not support this, and neither does the JVM. You can't solve this at the language level.



                      In general, the only way to prevent changes to an array is to not share the reference to the array with other code that might change it.



                      In your example, you have what is known as a leaky abstraction. You are passing an array to your Person class, and the caller is keeping a reference to that array so that it can change it. To solve this, you can:




                      • copy the array, and pass a reference to the copy, or

                      • have the constructor (or a setter for the array attribute) make the copy.


                      (See answer https://stackoverflow.com/a/55428214/139985 for example code.)



                      The second alternative is preferable from an OO perspective. The Person class should be responsible for preserving its own internal state from interference ... if that is your design requirement. It should not rely on the caller to do this. (Even if the caller is technically part of the same class as is the case here.)






                      share|improve this answer






























                        3














                        There is no such thing as immutable (unchangeable) array in Java. The Java language does not support this, and neither does the JVM. You can't solve this at the language level.



                        In general, the only way to prevent changes to an array is to not share the reference to the array with other code that might change it.



                        In your example, you have what is known as a leaky abstraction. You are passing an array to your Person class, and the caller is keeping a reference to that array so that it can change it. To solve this, you can:




                        • copy the array, and pass a reference to the copy, or

                        • have the constructor (or a setter for the array attribute) make the copy.


                        (See answer https://stackoverflow.com/a/55428214/139985 for example code.)



                        The second alternative is preferable from an OO perspective. The Person class should be responsible for preserving its own internal state from interference ... if that is your design requirement. It should not rely on the caller to do this. (Even if the caller is technically part of the same class as is the case here.)






                        share|improve this answer




























                          3












                          3








                          3







                          There is no such thing as immutable (unchangeable) array in Java. The Java language does not support this, and neither does the JVM. You can't solve this at the language level.



                          In general, the only way to prevent changes to an array is to not share the reference to the array with other code that might change it.



                          In your example, you have what is known as a leaky abstraction. You are passing an array to your Person class, and the caller is keeping a reference to that array so that it can change it. To solve this, you can:




                          • copy the array, and pass a reference to the copy, or

                          • have the constructor (or a setter for the array attribute) make the copy.


                          (See answer https://stackoverflow.com/a/55428214/139985 for example code.)



                          The second alternative is preferable from an OO perspective. The Person class should be responsible for preserving its own internal state from interference ... if that is your design requirement. It should not rely on the caller to do this. (Even if the caller is technically part of the same class as is the case here.)






                          share|improve this answer















                          There is no such thing as immutable (unchangeable) array in Java. The Java language does not support this, and neither does the JVM. You can't solve this at the language level.



                          In general, the only way to prevent changes to an array is to not share the reference to the array with other code that might change it.



                          In your example, you have what is known as a leaky abstraction. You are passing an array to your Person class, and the caller is keeping a reference to that array so that it can change it. To solve this, you can:




                          • copy the array, and pass a reference to the copy, or

                          • have the constructor (or a setter for the array attribute) make the copy.


                          (See answer https://stackoverflow.com/a/55428214/139985 for example code.)



                          The second alternative is preferable from an OO perspective. The Person class should be responsible for preserving its own internal state from interference ... if that is your design requirement. It should not rely on the caller to do this. (Even if the caller is technically part of the same class as is the case here.)







                          share|improve this answer














                          share|improve this answer



                          share|improve this answer








                          edited 36 mins ago

























                          answered 54 mins ago









                          Stephen CStephen C

                          525k72585944




                          525k72585944






























                              draft saved

                              draft discarded




















































                              Thanks for contributing an answer to Stack Overflow!


                              • Please be sure to answer the question. Provide details and share your research!

                              But avoid



                              • Asking for help, clarification, or responding to other answers.

                              • Making statements based on opinion; back them up with references or personal experience.


                              To learn more, see our tips on writing great answers.




                              draft saved


                              draft discarded














                              StackExchange.ready(
                              function () {
                              StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55428172%2fhow-to-prevent-changing-the-value-of-variable%23new-answer', 'question_page');
                              }
                              );

                              Post as a guest















                              Required, but never shown





















































                              Required, but never shown














                              Required, but never shown












                              Required, but never shown







                              Required, but never shown

































                              Required, but never shown














                              Required, but never shown












                              Required, but never shown







                              Required, but never shown







                              Popular posts from this blog

                              GameSpot

                              日野市

                              Tu-95轟炸機