What are method references?

Method references are a feature of Java 8 . The biggest addition in Java8 has been lambda expressions . Method Reference is the shorthand syntax for a lambda expression that executes just ONE method. It allows us to reference constructors or methods without executing them. Method references and Lambda are similar in that they both require a target type that consist of a compatible functional interface. An interface with only one method is called a functional interface. For example, Comparable, Runnable, AutoCloseable are some functional interfaces in Java. The double colon (::) operator is used for method reference. You can access a method (lambda expression) using the :: notation.
Integer::compare

A method reference can be used to point the following types of methods:

  1. Static methods
  2. Instance methods
  3. Constructors using new operator (TreeSet::new)
Example
import java.util.*; public class TestClass { public static void main(String[] args) { List weekDays = new ArrayList(); weekDays.add("Monday"); weekDays.add("Tuesday"); weekDays.add("Wednesday"); weekDays.add("Thursday"); weekDays.add("Friday"); weekDays.forEach(System.out::println); } }
Output

Monday

Tuesday

Wednesday

Thursday

Friday






Related Topics
  1. Java Interview Questions-Core Faq - 1
  2. Java Interview Questions-Core Faq - 2
  3. Java Interview Questions-Core Faq - 3
  4. Important features of Java
  5. Difference between Java and JavaScript?
  6. What is the difference between JDK and JRE?
  7. What gives Java its 'write once and run anywhere' nature?
  8. What is JVM and is it platform independent?
  9. What is Just-In-Time (JIT) compiler?
  10. What is the garbage collector in Java?
  11. What is NullPointerException in Java
  12. Difference between Stack and Heap memory in Java
  13. How to set the maximum memory usage for JVM?
  14. What is numeric promotion?
  15. Why do we need Generic Types in Java?
  16. What does it mean to be static in Java?
  17. What are final variables in Java?
  18. How Do Annotations Work in Java?
  19. How do I use the ternary operator in Java?
  20. What is instanceof keyword in Java?
  21. How ClassLoader Works in Java?
  22. What are fail-safe and fail-fast Iterators in Java
  23. "Cannot Find Symbol" compile error
  24. Difference between system.gc() and runtime.gc()
  25. How to convert TimeStamp to Date in Java?
  26. Does garbage collection guarantee that a program will not run out of memory?
  27. How setting an Object to null help Garbage Collection?
  28. How do objects become eligible for garbage collection?
  29. How to calculate date difference in Java
  30. Difference between Path and Classpath
  31. Is Java "pass-by-reference" or "pass-by-value"?
  32. Difference between static and nonstatic methods java
  33. Why Java does not support pointers?
  34. What is package in Java?
  35. What are wrapper classes?
  36. What is singleton class in Java?
  37. Difference between Java Local Variable, Instance Variable and a Class Variable?
  38. Can a top level class be private or protected in java
  39. Are Polymorphism , Overloading and Overriding similar concepts?
  40. How to Use Locks in Java
  41. Why Multiple Inheritance is Not Supported in Java
  42. Why Java is not a pure Object Oriented language?
  43. Why can't a Java class be declared as static?
  44. Difference between Abstract class and Interface in Java
  45. Why do I need to override the equals and hashCode methods in Java?
  46. Why does Java not support operator overloading?
  47. What’s meant by anonymous class in Java?
  48. Static Vs Dynamic class loading in Java
  49. Why am I getting a NoClassDefFoundError in Java?
  50. How to generate random integers within a specific range in Java
  51. What's the meaning of System.out.println in Java?
  52. What is the purpose of Runtime and System class?
  53. What is finally block in Java?
  54. What is difference between final, finally and finalize?
  55. What is try-with-resources in java?
  56. What is a stacktrace?
  57. What is the meaning of immutable in terms of String?
  58. What are different ways to create a string object in Java?
  59. Difference between String and StringBuffer/StringBuilder in Java
  60. What is the difference between creating String as new() and literal?
  61. How do I convert String to Date object in Java?
  62. How do I create a Java string from the contents of a file?
  63. What actually causes a StackOverflow error in Java?
  64. Why is char[] preferred over String for storage of password in Java
  65. What is I/O Filter and how do I use it in Java?
  66. Serialization and Deserialization in Java
  67. Understanding transient variables in Java
  68. What is Externalizable in Java?
  69. What is the purpose of serialization/deserialization in Java?
  70. What is the Difference between byte stream and Character streams
  71. How to append text to an existing file in Java
  72. Read/convert an InputStream to a String in Java
  73. What is the difference between Reader and InputStream in Java
  74. Introduction to Java threads
  75. What is synchronization Java?
  76. Static synchronization Vs non static synchronization in Java
  77. Java Thread Deadlock Tutorial
  78. What is Daemon thread in Java
  79. Difference between implements Runnable and extends Thread in Java
  80. What is the volatile keyword in Java
  81. What are the basic interfaces of Java Collections Framework
  82. What are the differences between ArrayList and Vector in Java
  83. What is the difference between ArrayList and LinkedList?
  84. What is the difference between List and Set in Java
  85. Difference between HashSet and HashMap in Java
  86. Difference between HashMap and Hashtable in Java?
  87. How does the hashCode() method of java works?
  88. Difference between capacity() and size() of Vector in Java
  89. What is a Java ClassNotFoundException?
  90. How to fix java.lang.UnsupportedClassVersionError