RootStatus.java

package com.yourapp;

import java.io.File;

public final class RootStatus {

    private static RootStatus instance;

    private final boolean rooted;

    private RootStatus(final boolean rooted) {
        this.rooted = rooted;
    }

    private static synchronized RootStatus getInstance() {

        if (instance == null) {
            final boolean rooted = hasSuExecutable();
            instance = new RootStatus(rooted);
        }
        return instance;
    }

    private static boolean hasSuExecutable() {
        return binaryExists("su");
    }

    private static boolean binaryExists(final String binaryName) {
        final String[] places = {"/sbin/", "/system/bin/", "/system/xbin/", "/data/local/xbin/",
                "/data/local/bin/", "/system/sd/xbin/", "/system/bin/failsafe/", "/data/local/"};
        for (final String where : places) {
            if (new File(where, binaryName).exists()) {
                return true;
            }
        }
        return false;
    }

    public static boolean isRooted() {
        return getInstance().rooted;
    }
}

YourActivity.java

package com.yourapp;

// imports

public class YourActivity extends Activity {
    
    public void onCreate(Bundle savedInstance) {
        
        if(Rootstatus.isRooted() ){
            // OH NO!
        } else {
            // All good.
        }
    }
}