Java lists and class inheritance

Question

List <Person> pers = new ArrayList<Person>();

pers.add(new Women("something1"));
pers.add(new Women("something2"));

pers.add(new Men("something1"));
pers.add(new Men("something2"));

System.out.println(pers); // prints everything

The classes Women and Men extend Person. After I store the data in my list how do I print only the Women or only the Men? Also how do I access attributes from the Women and Men?

With 2 lists works fine but I'm having trouble when I only have to use one list.

You could try using instanceof operator, but that usually means that your design is flawed. Why do you want to create only one list of peers? What is wrong with solution using two separate lists? — Pshemo
– Pshemo, Commented Oct 31, 2015 at 20:20
Well, if you need to distinguish men from women, you shouldn't store them in the same list. — JB Nizet
– JB Nizet, Commented Oct 31, 2015 at 20:21

Eric Guan · Accepted Answer · 2015-10-31 20:20:04Z

4

Use the instanceof keyword.

for(Person person : pers){
    if(person instanceof Women){
        System.out.println("I am a woman");
        int height = person.getHeight();
    }
    else if(person instanceof Men){
        System.out.println("I am a Man");
        int weight = person.getWeight();
    }
}

Once you know what type of object the person is, you can call any public variables/getters/setters on that object.

answered Oct 31, 2015 at 20:20

Eric Guan

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1 Comment

Ivana Over a year ago

Thanks , that helped. :)

Jason Woo · Accepted Answer · 2015-10-31 20:21:17Z

0

Object.getClass() will return the type of the object

answered Oct 31, 2015 at 20:21

Jason Woo

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