Why Lambda Expressions

Description

The lambda expressions allows us to pass logic in a compact way.

Example

The following code uses an anonymous inner class to add event handler for a button click action.

button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) { 
       System.out.println("hi");
    }//  w w  w  . jav a 2s.  c o m
});

The action handler prints out a message when that the button is clicked.

By using a lambda expression we can add the action handler to a button click event in a single line of code.

Note

Instead of passing in an inner class that implements an interface, we're passing in a block of code.

e is the name of a parameter,

-> separates the parameter from the body of the lambda expression.

In the lambda expression the parameter e is not declared with a type. javac is inferring the type of e from its context, the signature of addActionListener.

We don't need to explicitly write out the type when it's obvious. The lambda method parameters are still statically typed.