Java Tutorials - Herong's Tutorial Examples - Version 7.03, by Dr. Herong Yang

Java Tutorials - Herong's Tutorial Examples

∟Lambda Expressions and Method References

∟Lambda Expression as Method Reference

What Is Method Reference? A method reference is a shorthand form of a special lambda expression which contains only one static method invocation in the body. Of course, static method parameter list and return should match the base interface.

Here is the syntax of a method reference:

class_name :: method_name

The above method reference syntax is actually a shorthand form of the following lambda expression syntax:

(parameter_list) -> class_name.method_name(actual_parameter_list)

Comparing the two syntax, I can see that:

• The "parameter_list" is omitted in method reference. The compiler can get them by looking at the only abstract method of the base interface.
• The "->" is omitted in method reference. Because the "::" (double colon) token is introduced in method references as identifications of method references.
• The "class_name" and "method_name" are used method reference to identify which method to be invoked.
• The "actual_parameter_list" is omitted in method reference. The compiler will automatically pass all parameters from the "parameter_list" to the "actual_parameter_list in the same order.

Here is an example of a method reference:

ClassC :: methodM

The compiler will process the above method reference like the following lambda expression:

(TypeA a, TypeB b) -> ClassC.methodM(a, b)

Of course, we are assuming that the base interface has to following abstract method:

public TypeC c methodI(TypeA a, TypeB b);

See the next section for an example program that uses method references.

Last update: 2014.

Table of Contents

 About This Book

 Installing JDK 1.8 on Windows

 Execution Process, Entry Point, Input and Output

 Primitive Data Types and Literals

 Bits, Bytes, Bitwise and Shift Operations

 Managing Bit Strings in Byte Arrays

 Reference Data Types and Variables

 StringBuffer - The String Buffer Class

 System Properties and Runtime Object Methods

 Generic Classes and Parameterized Types

 Generic Methods and Type Inference

►Lambda Expressions and Method References

 What Is Lambda Expression?

 LambdaCalculator.java - Lambda Expression Example

 Lambda Expression Syntax Options

►Lambda Expression as Method Reference

 Method Reference Example - LambdaMethodRefernce.java

 Lambda Expression Stream Pipeline Operations

 Execution Threads and Multi-Threading Java Programs

 ThreadGroup Class and "system" ThreadGroup Tree

 Synchronization Technique and Synchronized Code Blocks

 Deadlock Condition Example Programs

 Garbage Collection and the gc() Method

 Outdated Tutorials

 References

 PDF Printing Version

Lambda Expression as Method Reference - Updated in 2018, by Dr. Herong Yang