Advanced Java

Consider a situation where you desire all List elements to be printed. This could be explained by the given code:

Java Code: This is the code to explain printing of all elements

public void processElements(List<Object> elements){
   for(Object o : elements){
      System.out.println(o);
   }
}

This method couldn’t be used along with List<String> instance. To sort out this problem, wildcard operator is used. For writing generic List by the help of wildcard operator, use this code.

Java Code: This is the code to explain wildcard operator

List<?> listOfUnknown = new ArrayList<?>();    
//ProcessElements() method could be defined as following: 
public void processElements(List<?> elements){
   for(Object o : elements){
      System.out.println(o);
   }
}
//ProcessElements() could be called with any kind of generified List instance. For Example: 
List<String> elements = new ArrayList<String>
// ... add String elements to the list.
processElements(elements);