CODEWITHSUNDEEP
javainheritance
Kevin
Kevin

Reputation: 6292

Copy fields from its parent class in Java

I have a question regarding Java class fields.

I have two Java classes: Parent and Child

class Parent{
    private int a;
    private boolean b;
    private long c;

    // Setters and Getters
    .....
}


class Child extends Parent {
    private int d;
    private float e;

    // Setters and Getters
    .....
}

Now I have an instance of the Parent class. Is there any way to create an instance of the Child class and copy all the fields of the parent class without calling the setters one by one?

I don't want to do this:

   Child child = new Child();
   child.setA(parent.getA());
   child.setB(parent.getB());
   ......

Also, the Parent does not have a custom constructor and I cannot add constructor onto it.

Please give you opinions.

Many thanks.

Upvotes: 21

Views: 17418

Answers (5)

mwikblom
mwikblom

Reputation: 361

Have you tried, using apache lib?

BeanUtils.copyProperties(child, parent)

http://commons.apache.org/beanutils/apidocs/org/apache/commons/beanutils/BeanUtils.html

Upvotes: 33

rcorbellini
rcorbellini

Reputation: 1337

you can use reflection i do it and work fine for me:

 public Child(Parent parent){
    for (Method getMethod : parent.getClass().getMethods()) {
        if (getMethod.getName().startsWith("get")) {
            try {
                Method setMethod = this.getClass().getMethod(getMethod.getName().replace("get", "set"), getMethod.getReturnType());
                setMethod.invoke(this, getMethod.invoke(parent, (Object[]) null));

            } catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException ex) {
                //not found set
            }
        }
    }
 }

Upvotes: 7

adrian
adrian

Reputation: 131

Did you try do this due reflection? Technicaly you invoke setters one by one but you don't need to know all names of them.

Upvotes: 1

SJuan76
SJuan76

Reputation: 24780

You can create a Child constructor that accepts a Parent. But there, you will have to set all the values one by one (but you can access the Child attributes directly, without set).

There is a workaround with reflection, but it only adds complication to this. You don't want it just for save some typing.

Upvotes: 0

pcalcao
pcalcao

Reputation: 15965

You can set your fields as protected instead of private and access them directly on the child class. Does that help?

Upvotes: 0

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