First class functions Vs Higher order functions

First class functions means the ability to treat a function as a value, assigning it to a variable, or passing it as an argument to another function.

 //example 1 assignment  
   Function<String,String> postfixFunction = s -> s + "-postfix";  
 //example 2 passing as parameter  
   public void someMethod() {  
     stringManipulator(postfixFunction, asList("A","B"));  
   }  

A higher order function is a function that accepts other functions as arguments, or returns another function.

  //example 1 accepting function as arguments  
   public List<String> stringManipulator(Function<String, String> manipulator, List<String> data) {  
     return data.stream().map(manipulator).collect(toList());  
   }  
   //example 2 returning a function  
   public Function<String, String> postfixFunction() {  
     return s -> s + "-postfix";  
   }