want to create a map<String , Object> ,Object can be String and can be class Object

Question

How want to create a Map<String , Object>.

In this map everytime the Object is a string. But Now I want to put a class in the object in addition to that. Is this a good way to mix string and a class object? If yes, when I iterate through the map, how can I distiguish between class and string?

Answer 1

Map<String, Object> map = new HashMap<String, Object>();
...
for (Map.Entry<String, Object> entry : map.entrySet()) {
    if (entry.getValue() instanceof String) {
        // Do something with entry.getKey() and entry.getValue()
    } else if (entry.getValue() instanceof Class) {
        // Do something else with entry.getKey() and entry.getValue()
    } else {
        throw new IllegalStateException("Expecting either String or Class as entry value");
    }
}

Answer 2

Every objects (excluding interfaces) in java extends Object, so your approach is correct.

To know whether an object is a string or other object type, use the instanceof keyword.

Example:

Map<String, Object> objectMap = ....;

for (String key :  objectMap.keySet()) {
    Object value = objectMap.get(key);
    if (value instanceof String) {
        System.out.println((String) value);
    } else if (value instanceof Class) {
        System.out.println("Class: " + ((Class)value).getName());
    }
}