Yes that’s correct – You need to implement clone() (or another suitable mechanism for copying your object, as clone() is considered “broken” by many programmers). Your clone() method should perform a deep copy of all mutable fields within your object. That way, modifications to the cloned object will not affect the original. In your example … Read more
You cannot create an array of a generic type. Instead, you can create an ArrayList<ArrayList<String>>.
Use ArrayList.addAll(). Something like this should work (assuming lists contain String objects; you should change accordingly). List<String> combined = new ArrayList<String>(); combined.addAll(firstArrayList); combined.addAll(secondArrayList); combined.addAll(thirdArrayList); Update I can see by your comments that you may actually be trying to create a 2D list. If so, code such as the following should work: List<List<String>> combined2d = new … Read more
It’s because, List returned by subList() method is an instance of ‘RandomAccessSubList’ which is not serializable. Therefore you need to create a new ArrayList object from the list returned by the subList(). List<String> list = new ArrayList<String>(originalList.subList(0, 10));
How about this: new ArrayList<T>(set); For Java 7 and later, this can be simplified, as type arguments <T> can be replaced with diamond type <>: new ArrayList<>(set);
When someone writes code like this, he/she is trying to follow a basic OO design principle which says – Program to an interface, not to a concrete implementation I have explained this principle in one of my blog posts. Look in the Class Inheritance VS Interface Inheritance section. To summarize the post, when you use … Read more
Your uniqueRecs has String type of the key. You have to do: List<String> keys = new ArrayList<>(uniqueRecs.keySet()); or List<ARecord> values = new ArrayList<>(uniqueRecs.values());
OK, I’ve done some research. If you create the following hierarchy: public interface One { void DoIt(); } public interface Two : One { void DoItMore(); } public class Magic : Two { public void DoItMore() { throw new NotImplementedException(); } public void DoIt() { throw new NotImplementedException(); } } And compile it, then reference … Read more
Below code should work for your case. List<Customer> customerList = CustomerDB.selectAll(); Gson gson = new Gson(); JsonElement element = gson.toJsonTree(customerList, new TypeToken<List<Customer>>() {}.getType()); if (! element.isJsonArray() ) { // fail appropriately throw new SomeException(); } JsonArray jsonArray = element.getAsJsonArray(); Heck, use List interface to collect values before converting it JSON Tree.