12 Lambda Expressions
and Streams
and Streams
Write a statement lambda
Write an expression lambda
The Java™ Tutorials
Java Lambda Expressions Jenkov
Streams tutorialspoint
Videos
Java Lambda Expressions #1 - The Basics (15:57) Jenkov
Java Streams API #1 - The Basics (17:57)
Implement functional interfaces using lambda expressions, including interfaces from the java.util.function package
Use Java Streams to filter, transform and process data
Perform decomposition and reduction, including grouping and partitioning on sequential and parallel streams
Use local variable type inference, including as lambda parameters
No Oracle Academy this week
17 Java SE 8 Lambdas and Streams
Lambda Practice
Mindfulness
Previous week review
Functional interface implementation
Anonymous class
Resource reinforcement and clarification
Lambda Expressions
you can consider lambda expressions as anonymous methods
pass functionality as an argument to another method
can replace an anonymous inner class method
Discussion: Compare and contrast functional programming and object-oriented programming.
AWS Lambda - same word, different but somewhat related concept
Project
Database
Review the original interface on the bottom of the Encapsulation page. It had this code
interface MyInterface {
public void printIt(String text);
}
and
class MyInterfaceImplementation implements MyInterface {
@Override
public void printIt(String text) {
System.out.println(text);
}
}
MyInterfaceImplementation mii = new MyInterfaceImplementation();
mii.printIt("Lame way");
Review the anonymous interface implementation on the bottom of the Lists page.
It had this code:
MyInterface mi2 = new MyInterface() {
public void printIt(String text){
System.out.println(text);
}
};
mi2.printIt("Anonymous way");
Code written using an anonymous interface implementation can be converted to a lambda expression using the format: parameters, arrow, body. Wild!
This format (with braces) is called a "statement lambda".
MyInterface mi3 = (String text) -> {
System.out.println(text);
};
mi3.printIt("Cool lambda way");
Parameter type can be omitted. Really Wild!
MyInterface mi4 = (text) -> {
System.out.println(text);
};
mi4.printIt("Cooler way");
When it's just one line, the braces and semicolon can be omitted. Super Wild!
This format (without braces) is called an "expression lambda".
MyInterface mi5 = (text) ->
System.out.println(text);
mi5.printIt("Coolest way");
When a lambda expression takes a single parameter, you can also omit the parentheses. Wild(!)
MyInterface mi6 = text ->
System.out.println(text);
mi6.printIt("Cooler than cool");
When a lambda expression does nothing but call an existing method the expression lambda can be replaced with a method reference. Mind == Blown!
MyInterface mi7 = System.out::println;
mi7.printIt("Ice cold");