Which Java Design Pattern fits best for if-else statement including loop?

Question

I have a use case with 7-8 if else. Sample use case:

 String type;
 List < Entity > entityList;


 if (type.equals(\"A\")) {
    ClassA a = new ClassA();
          


        

Answer 1

Introduce an interface for all tasks and use a factory pattern. The factory can use a map internally. E.g.

public class TaskFactory {

    private Map> taskTypeMap = new HashMap>();

    public TaskFactory() {
        taskTypeMap.put("A", ATask.class);
        taskTypeMap.put("B", BTask.class);
    }

    public Task createTask(String type) {
        Class taskType = taskTypeMap.get(type);

        if (taskType == null) {
            throw new IllegalArgumentException("Task type " + type
                    + " is not supported");
        }

        try {
            return taskType.newInstance();
        } catch (Exception e) {
            throw new IllegalStateException(
                    "Unable to instantiate Task of type " + taskType, e);
        }
    }

}

Your client code will then change to

String type = ...;
List entityList = ...;

TaskFactory taskFactory = new TaskFactory();
Task task = taskFactory.createTask(type);

task.performTask();

for (Entity e: entitylist) {
    // do some task
}