Overriding compareTo(T t)

Question

I did a class "People" which has a String name. Now I want to compare two objects using TreeSet.

public class People<T> implements Comparable<T> {

    public TreeSet<People> treeSet;
    public String name;

    public People(String name)
    {
        treeSet =  new TreeSet();
this.name = name;
    }

.....

@Override
    public int compareTo(T y) {

        if(this.name.equals(y.name)) blablabla; //Here I get error 
    }

Error:

Cannot find symbol
symbol: variable name;
location: variable y of type T
where T is a type variable 
T extends Object declared in class OsobaSet

Does anyone know how to solve the problem?

Nothing tells the compiler, that _T_ type has a _name_ field . — Arnaud, Jan 20 '16 at 09:44
I guess it should be `implements Comparable` because that is what you want to compare. And then the compiler knows that People has a `name` Field ... — Fildor, Jan 20 '16 at 09:46
Have a look at this answer: http://stackoverflow.com/a/3718515/982149 — Fildor, Jan 20 '16 at 09:49

AdamSkywalker · Accepted Answer · 2016-01-20T10:14:07.320

5

Generic type in Comparable interface stands for the type of objects that will be compared.

This is correct usage for your example:

public class People implements Comparable<People>

In this case method signature will be

@Override
public int compareTo(People y) {
    if (this.name.equals(y.name))  { ...
}

edited Jan 20 '16 at 10:14

answered Jan 20 '16 at 10:07

AdamSkywalker

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Overriding compareTo(T t)

1 Answers1