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I have 2 objects in Java, person1 and person2. With a event button in the code I say that person2 = person1, then I need to change the age of person 1 without change person2.

Person objperson1 = new Person();
objperson1.setAge(30);
Person objperson2 = new Person();
objperson2 = objperson1;
objperson1.setAge(40);
System.out.println(objperson2.getAge()); //console print 40. I need it print 30

try this:

 public class Demo {

    public static void main(String args[]) throws CloneNotSupportedException{

    Person p1=new Person();
    p1.setAge(30);


    Person p2 = (Person) p1.clone();
    p1.setAge(40);
    System.out.println(p2.getAge());//30

    }
    }

    class Person implements Cloneable{

    private int age;

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        // TODO Auto-generated method stub
        return (Person)super.clone();  
    }
}

4. Methods Use Instance Variables: How Objects Behave, Selection from Head First Java, 2nd Edition [Book] Can every object of that type have different method behavior? Change the value of z inside the method. Java is call by value and there are no pointers; but the advantages of having a class is that they are bound by the objects, and calling on specific objects telieve you from needing to call them with reference. And moreover, if you are passing on an object as the parameter of that function then I don't see

objperson1 and objperson2 are two reference variables pointing to the same Person object.

If you want a copy of objperson1 you could use:

 Person objperson2 = (Person) objperson1.clone();

changing the value of String object in java, Let's look at this for a minute or two So you are running some code and expect a string return to tell you how it went. In doing this you noticed  The Value Objects pattern transforms values in our projects into real objects, giving us more type safety, hiding implementation, and housing all related logic.

I think this stems from a misunderstanding on what's happening in Java. When you say objperson2 = objperson1;, you're telling it to assign the name objperson2 to point to the object that objperson1 is referencing. So it's like assigning another name to the same thing. In other words, let's say your name (objperson1) was Patrick. If I say "I'm going to call you Pat from now on" (objperson2=objperson1), and I then say "Pat, pass me the salt", I would expect you to pass me the salt, because both names point to you. So you need to create two different objects (like having two different people) with two different names.

To do a copy like this, you'd be looking at preforming a "deep copy". The question should be, "Is this really necessary for you to do?" It's relatively rare to need to do this, so I would question your implementation and reconsider how you're coding the problem.

Replace Data Value with Object, With replacement of a data value with an object, we have a primitive field (​number, string, etc.) that's no longer so simple due to growth of the program and now has  Although Java is strictly pass by value, the precise effect differs between whether a primitive type or a reference type is passed. When we pass a primitive type to a method, it is passed by value. But when we pass an object to a method, the situation changes dramatically, because objects are passed by what is effectively call-by-reference.

implement clone to your object

 public class Person implements Cloneable{

    private String age;
    public Person(){
    }
    public void setStr(String age){
        this.age = age;
    }
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

Clone object

Person per = new Person();

Person delTemp = (Person ) per.clone();

How to replace existing element in ArrayList, Java program to update arraylist object and set value at index. Replace element example. public class ArrayListExample. {. The second line moves rectTwo because the move () method assigns new values to the object's origin.x and origin.y. As with instance fields, objectReference must be a reference to an object. You can use a variable name, but you also can use any expression that returns an object reference.

Year code:

objperson2 = objperson1;

means that objperson2 variable has link on objperson1 object now. In your case you need to make a copy of objperson1 and apply it to objperson2 variable. You can do it like this:

objperson2 = objperson1.clone();

But keep in mind that you must to implement clone mechanism for custom object. Example:

public class Person implements Cloneable {

    private int age;

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public Person clone() throws CloneNotSupportedException {
        Person copy = new Person();
        copy.age = this.age; // (example deep clone for custom properties) or just use Person copy = super.clone();

        return copy;
    }
}

Use:

Person objperson1 = new Person();
        objperson1.setAge(30);        
        Person objperson2 = objperson1.clone();
        objperson1.setAge(40);
        System.out.println(objperson2.getAge());

Day 4 -- Working with Objects, Changing Values. Assigning a value to that variable is equally easy-just tack an assignment operator on the right side of the  In Java, the new keyword is used to create new objects. There are three steps when creating an object from a class − Declaration − A variable declaration with a variable name with an object type.

Does Java pass by reference or pass by value?, You may also wonder how Java manages object values in the memory If you determined that the value would change to 30, you are correct. Changing the value of Array in Java. This is very simple of one dimensional array program. In this tutorial you will learn how to change array values. The one dimensional array program is provided Java application program about the explanation with Java Source code. This is very simple of one dimensional array program.

Understanding Class Members (The Java™ Tutorials > Learning the , Any object can change the value of a class variable, but class variables can also be manipulated without creating an instance of the class. For example, suppose  Well here’s how to do it as requested: [code]// initial data var books = { "History": [ {"Number": "AD-3424"}, {"Number": ";AD-3424"} ] }; // changing the

Java is Pass by Value and Not Pass by Reference, Notice that we are changing values of o1 and o2 but they are copies of “red” and “blue” reference locations, For objects, Java is pass-reference-by-value. Getting all values with getString can be very useful, but it also has its limitations. For instance, if it is used to retrieve a numeric type, getString converts the numeric value to a Java String object, and the value has to be converted back to a numeric type before it can be operated on as a number. In cases where the value is treated as a

Comments
  • try cloning the Object
  • objperson2 = objperson1; - Now you no longer have two objects, but only one.
  • implement cloneable interface
  • or a decent copy, instead of assignment. but first step: question your logic: "I say that person2 = person1, then I need to change the age of person 1 without change person2." how is this supposed to make sense?
  • @Lokesh possible, but having a decent grasp and understanding of logic is a requirement to be able to start programming, seeing as he's already doing that .. If I thought the problem was (just) with his OO skills, I would question the use of storing an 'age' for a person