//Init the SharedPreferences instance.
SharedPreferences sharedPreferences = this.getApplicationContext().getSharedPreferences("com.your.package.name", Context.MODE_PRIVATE);

//Grab a map of all keys within SharedPreferences.
Map<String, ?> keysMap = sharedPreferences.getAll();

/*
 * So like I said in my previous text, you should put a prefix before your blocked apps' package names. For the sake of this example,
 * let's assume that the prefix is "PKG_STATUS". What we need to do now is iterate through keysMap and add all keys which contain the
 * prefix to a list.
 */
String prefix = "PKG_STATUS";
ArrayList<String> packagesList = new ArrayList<String>();

//Iterate through the Map.
for (Map.Entry<String, ?> entry : keysMap.entrySet()) {
    //Check if the package name starts with the prefix.
    if (entry.startsWith(prefix)) {
        //Add JUST the package name (trim off the prefix).
        packagesList.add(entry.substring(prefix.length()));
    }
}

//packagesList should now contain a a list of all your packages in SharedPreferences!