Predicate Interface

1. Predicate is a mathematics term to introduce java 8 as a functional interface. version (i.e.,Predicate<T>). 
2. Predicate is  a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
3. A predicate is a function with a single argument and returns boolean value. 
4. Predicate interface present in Java.util.function package.
5. It’s a functional interface and it contains only one method i.e., test()

      Syntex.

                           interface Predicate<T> {   

                                        public boolean test(T t);                

                             }
         

     Method Detail

                 public boolean test(T t); 

    Parameters
                  T - the type of arguments to the predicate                  
                  t - the input argument.
    Returns

                 True if the input argument matches the predicate, otherwise false.

         As predicate is a functional interface and hence it can refers lambda expression. 

   Example: 1. 
      Write a predicate to check whether the given integer is greater than 10 or not. 

                       public boolean test(Integer I) { 
                             if (I >20) { 
                                ⇩⇩  return true; 
                              }
                              else { 
                                   return false; 
                              }
                            }
                                   
                                     ⇓
                        (Integer I) -> {
                                      if(I > 20 )
                                          return true;
                                      else 
                                          return false;
                                       }

                                      ⇓
                                 I ->(I > 20);
                                     
                                      ⇓
                            predicate<Integer> p = I (I >20); 
                            System.out.println (p.test(100)); true 
                            System.out.println (p.test(17)); false 

Example 1:
                     class Test { 
                           public static void main(String[] args) {   
                                  predicate<Integer> p = I  (i>10); 
                                   System.out.println(p.test(100)); 
                                   System.out.println(p.test(17)); 
                                   System.out.println(p.test(true)); //Compile time error                                    }
                               }

Example 2.Write a predicate to check the length of given string is greater than 5 or not.
         

     
 Example 3: Write a predicate to check whether the given collection is empty or not. 

        

 Predicate Joining:-

  It’s possible to join predicates into a single predicate by using the following methods.

1. and()  
2. or()  
3. negate()

 these are exactly same as logical AND ,OR complement operators.

Example 4: How to use Predicate in Functional interface

Output:-

The Numbers Greater Than 10:
15
20
25
30
The Even number are :
0
10
20
30
The number not Greater then 10:
0
5
10
The number Greater then 10  and Even are:
20
30
The number Greater then or Even are
0
10
15
20
25
30


 Example 4: To Display names starts with 'K' by using Predicate.

Output:-

The name Start with K are :
Kareena
Kajal
Kareena
Katrina

Example 5: To remove null values and empty strings from the given list.

Output:- The List of valid Name : [Sudhir, Ram, Kajal, Monika, Kareena, Katrina]


Example 6: User Authentication by using Predicate

Output:-
Enter the Username :
Sudhir
Enter the Password :
sudhir

Valid user and can avail all services

Example 7: To check whether SoftwareEngineer is allowed into pub or not by using Predicate

Output:-
The Allowed number into Pub are :
Sudhir
Sudhir
Asha
Aarti

Example 8: Employee Management Application.

Output:-
Manager Information :
[Rakest,Developer,40000.00,Bangalore]
**************************************************
Bangalore Employees Information:
[Sudhir,Team Lead,30000.00,Bangalore]
[Aarti,Test Engineer,30000.00,Bangalore]
[Rakest,Developer,40000.00,Bangalore]
**************************************************
[[Sudhir,Team Lead,30000.00,Bangalore], [Aarti,Test Engineer,30000.00,Bangalore], [Rakest,Developer,40000.00,Bangalore], [Manish,Software Engineer,20000.00,Hyderabad], [Neha,Operation Manager,50000.00,Hyderabad], [Ram,ECO,300000.00,Patna]]

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Sudhir Kumar