Lamdas

What are lambdas?

The Java programming language supports lambdas as of Java 8. A lambda expression is a block of code with parameters. Lambdas allows to specify a block of code which should be executed later. If a method expects a functional interface as parameter it is possible to pass in the lambda expression instead.

The type of a lambda expression in Java is a functional interface.

Purpose of lambda expressions

Using lambdas allows to use a condensed syntax compared to other Java programming constructs. For example theCollection interfaces has forEach method which accepts a lambda expression.

List<String> list = Arrays.asList("microsoft.com","google.com","heise.de" )list.forEach(s-> System.out.println(s));

20.3. Using method references

You can use method references in a lambda expression. Method reference define the method to be called viaCalledFrom::method. CalledFrom can be * instance::instanceMethod * SomeClass::staticMethod * SomeClass::instanceMethod

List<String> list = new ArrayList<>();
list.add("microsoft.com");
list.add("google.com");
list.add("heise.de");
list.forEach(System.out::println);

20.4. Difference between a lambda expression and a closure

The Java programming language supports lambdas but not closures. A lambda is an anonymous function, e.g., it can be defined as parameter. Closures are code fragments or code blocks which can be used without being a method or a class. This means that a closure can access variables not defined in its parameter list and that it can also be assigned to a variable.