Getting Error in importing libraries

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Java

Mobile

Android

in the following code i am getting error in importing libraries, what edit in libraries i should do?
its giving error in importing of FragmentStatePagerAdapter

package widget;

/**
 * Created by ramneekkashyap on 16/08/15.
 */
import android.app.Fragment;
import android.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;

import app.SubredditListFragment;
import app.ThingListFragment;

public class SearchPagerAdapter extends FragmentStatePagerAdapter {

    private final String accountName;
    private final String query;

    public SearchPagerAdapter(FragmentManager fm, String accountName, String query) {
        super(fm);
        this.accountName = accountName;
        this.query = query;
    }

    @Override
    public int getCount() {
        return 2;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return ThingListFragment.newInstance(accountName, null, 0, query, 0);

            case 1:
                return SubredditListFragment.newInstance(accountName, null, query, 0);

            default:
                throw new IllegalArgumentException();
        }
    }
}