Part 2
Interview questions on Java 8 Function Functional Interface for experienced covered in this post:
What are the default methods defined in Function functional
interface?
-
There are a couple of default methods inside the Function interface.
1.
andThen(): f1 will be applied first and then f2.
|
package simplifiedjava.crackedInterview.java8; import java.util.function.Function; public class FunctionInterfaceDemo {
public
static
void
main(String[] args) {
Function<String, Integer> f1
= s
-> s.length();
Function<String, String> f2
= s
-> s.toUpperCase();
Function<String, String> f3
= s
-> s.toLowerCase(); Function<String, String> f4 = f3.andThen(f2);
System.out.println(f1.apply("Simplify Java"));
System.out.println(f2.apply("Simplify Java"));
System.out.println(f3.apply("Simplify Java"));
System.out.println(f4.apply("Simplify Java"));
}
}
Output:
13
SIMPLIFY JAVA
simplify java
SIMPLIFY JAVA |
2.
compose(): f2 will be applied fist and then f1.
|
package simplifiedjava.crackedInterview.java8;
import
java.util.Arrays;
import
java.util.List; import java.util.function.Function; public class FunctionInterfaceDemo {
public
static
void
main(String[] args) { List<Integer> list = Arrays.asList(10,20,30,40,50);
Function<Integer, Integer> f1
= n
-> n
+ 10;
Function<Integer, Integer> f2
= n
-> n
* 2; Function<Integer, Integer> f3 = f1.compose(f2);// f2 will execute first and then f1
for(Integer i
: list) {
System.out.println(f3.apply(i));
}
}
}
Output:
30 [10 = (10*2) + 10
= 30]
50 [20 = (20*2) + 10
= 50]
70 [30 = (30*2) + 10
= 70]
90 [40 = (40*2) + 10
= 90]
110 [50 = (50*2) + 10 = 100] |
What is the static method defined in
Function functional interface?
-
There is only one static method defined inside the Function
interface.
-
Identity() static method is defined in Function.
-
Returns a function that always returns its input argument.
-
You will get the same output as your input.
-
Please refer to the below example.
|
package simplifiedjava.crackedInterview.java8;
import
java.util.Arrays;
import
java.util.List; import java.util.function.Function; public class FunctionStaticMethodDemo {
public
static
void
main(String[] args) {
List<String> list
= Arrays.asList(".Net","Php","Java","C++","C","Database");
Function<String, String> f
= Function.identity();
for(String s: list) {
System.out.println(f.apply(s));
}
}
}
Output:
.Net
Php
Java
C++
C
Database |
 
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What is the difference between
Predicate and Function interface?
|
|
Predicate |
Function |
|
1. |
The predicate can return only a Boolean value. |
The function can return any type of object. |
|
2. |
Predicate defined one abstract method. i.e. test() method. |
The function defined one abstract method. i.e. apply()
method. |
|
3. |
Public Boolean test(T t); |
Public R apply(T t, R r); |
|
4. |
The predicate can take only one type of parameter which represent
the input argument. |
Function interface takes two parameters. The first one represents
input type and the second one represent return type. |
|
5. |
Predicate<T> |
Function<T,R> |
-
Java interview questions and answers all MNC - Click here
-
Basic core java interview questions and answers for freshers - Click here
-
Core java interview questions for 3 years experience - Click here
-
Core java interview questions and answers for 3-5 years exp - Click here
-
Core java interview questions and Answers for 5 - 7 Years exp - Click here
-
Basic Java Interview Questions and Answers - Click here
-
Java interview questions and answers on oops - Click here
-
Java interview questions and answers on Strings - Click here
-
Java interview questions on exception handling - Click here
-
Interview questions on multithreading in java for experienced - Click here
-
Interview questions on serialization in java for experienced
- Click here
-
Interview questions on inner class in java for experienced
- Click here
-
Interview questions on Collections in java for experienced
- Click here
|
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