Can I add new methods to the String class in Java?

Question

I\'d like to add a method AddDefaultNamespace() to the String class in Java so that I can type \"myString\".AddDefaultNamespace() instead of

Answer 1

People searching with keywords "add method to built in class" might end up here. If you're looking to add method to a non final class such as HashMap, you can do something like this.

public class ObjectMap extends HashMap {

    public Map map;

    public ObjectMap(Map map){
        this.map = map;
    }

    public int getInt(String K) {
        return Integer.valueOf(map.get(K).toString());
    }

    public String getString(String K) {
        return String.valueOf(map.get(K));
    }

    public boolean getBoolean(String K) {
        return Boolean.valueOf(map.get(K).toString());
    }

    @SuppressWarnings("unchecked")
    public List getListOfStrings(String K) {
        return (List) map.get(K);
    }

    @SuppressWarnings("unchecked")
    public List getListOfIntegers(String K) {
        return (List) map.get(K);
    }

    @SuppressWarnings("unchecked")
    public List> getListOfMapString(String K) {
        return (List>) map.get(K);
    }

    @SuppressWarnings("unchecked")
    public List> getListOfMapObject(String K) {
        return (List>) map.get(K);
    }

    @SuppressWarnings("unchecked")
    public Map getMapOfObjects(String K) {
        return (Map) map.get(K);
    }

    @SuppressWarnings("unchecked")
    public Map getMapOfStrings(String K) {
        return (Map) map.get(K);
    }
}

Now define a new Instance of this class as:

ObjectMap objectMap = new ObjectMap(new HashMap();

Now you can access all the method of the built-in Map class, and also the newly implemented methods.

objectMap.getInt("KEY");

EDIT:

In the above code, for accessing the built-in methods of map class, you'd have to use

objectMap.map.get("KEY");

Here's an even better solution:

public class ObjectMap extends HashMap {

    public ObjectMap() {

    }

    public ObjectMap(Map map){
        this.putAll(map);
    }

    public int getInt(String K) {
        return Integer.valueOf(this.get(K).toString());
    }

    public String getString(String K) {
        return String.valueOf(this.get(K));
    }

    public boolean getBoolean(String K) {
        return Boolean.valueOf(this.get(K).toString());
    }

    @SuppressWarnings("unchecked")
    public List getListOfStrings(String K) {
        return (List) this.get(K);
    }

    @SuppressWarnings("unchecked")
    public List getListOfIntegers(String K) {
        return (List) this.get(K);
    }

    @SuppressWarnings("unchecked")
    public List> getListOfMapString(String K) {
        return (List>) this.get(K);
    }

    @SuppressWarnings("unchecked")
    public List> getListOfMapObject(String K) {
        return (List>) this.get(K);
    }

    @SuppressWarnings("unchecked")
    public Map getMapOfObjects(String K) {
        return (Map) this.get(K);
    }

    @SuppressWarnings("unchecked")
    public Map getMapOfStrings(String K) {
        return (Map) this.get(K);
    }

    @SuppressWarnings("unchecked")
    public boolean getBooleanForInt(String K) {
        return Integer.valueOf(this.get(K).toString()) == 1 ? true : false;
    }
}

Now you don't have to call

objectMap.map.get("KEY");

simply call

objectMap.get("KEY");