Question

I write a simple class (the merit of StringPools themselves is not my question; I have specific reasons for wanting this class):

import java.lang.ref.WeakReference;
import java.util.WeakHashMap;

public final class StringPool {

    private WeakHashMap m_pool = new WeakHashMap();

    public String intern(String s) {
        WeakReference reference = (WeakReference)m_pool.get(s);
        if(reference != null) {
            String interned = (String)reference.get();
            if(interned != null)
                return interned;
        }
        m_pool.put(s,new WeakReference(s));
        return s;
    }
};

When I compile it, the compiler notes it uses unchecked or unsafe operations:

warning: [unchecked] unchecked call to WeakReference(T) as a member of the raw type WeakReference       
    m_pool.put(s,new WeakReference(s));
    ^   where T is a type-variable:
    T extends Object declared in class WeakReference 

warning: [unchecked] unchecked call to put(K,V) as a member of the raw type WeakHashMap 
    m_pool.put(s,new WeakReference(s));
    ^   where K,V are type-variables:
    K extends Object declared in class WeakHashMap
    V extends Object declared in class WeakHashMap

2 warnings

How should I fix these warnings so the code compiles clean and is correct?

Answer 1

Add generics:

WeakHashMap<String, WeakReference<String>>

remove casting from:

(WeakReference)m_pool.get(s);

and:

(String)reference.get()

to look like:

m_pool.get(s);

and

reference.get()

respective.