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Method Reference
Last Updated : 26 May, 2026
title: Method Reference in Java 8
Java 8 Features77 words6 headingsTables includedExamples included
title: Method Reference in Java 8 description: Method reference :: operator ka use
Lambda expression ka shorthand jab sirf ek method call karna ho.
4 Types
1. Static Method Reference
java exampleWoHoTech
// Lambda
Function<String, Integer> parse = s -> Integer.parseInt(s);
// Method Reference
Function<String, Integer> parse = Integer::parseInt;
parse.apply("123"); // 123
// Another example
List<String> nums = Arrays.asList("1", "2", "3");
nums.stream().map(Integer::parseInt).forEach(System.out::println);2. Instance Method Reference (Specific Object)
java exampleWoHoTech
String str = "Hello World";
// Lambda
Supplier<String> upper = () -> str.toUpperCase();
// Method Reference
Supplier<String> upper = str::toUpperCase;
upper.get(); // "HELLO WORLD"3. Instance Method Reference (Arbitrary Object)
java exampleWoHoTech
// Lambda
Function<String, String> upper = s -> s.toUpperCase();
// Method Reference
Function<String, String> upper = String::toUpperCase;
List<String> names = Arrays.asList("ram", "shyam");
names.stream().map(String::toUpperCase).forEach(System.out::println);
// Comparator
List<String> sorted = names.stream()
.sorted(String::compareToIgnoreCase)
.collect(Collectors.toList());4. Constructor Reference
java exampleWoHoTech
// Lambda
Supplier<ArrayList> listMaker = () -> new ArrayList();
// Method Reference
Supplier<ArrayList> listMaker = ArrayList::new;
// With parameter
Function<String, StringBuilder> sbMaker = StringBuilder::new;
sbMaker.apply("Hello"); // new StringBuilder("Hello")
// Collect to list using constructor reference
Stream<String> stream = Stream.of("a", "b", "c");
List<String> list = stream.collect(Collectors.toCollection(ArrayList::new));Comparison Table
| Type | Lambda | Method Reference |
|---|---|---|
| Static | s -> Integer.parseInt(s) | Integer::parseInt |
| Instance (specific) | () -> obj.method() | obj::method |
| Instance (arbitrary) | s -> s.toUpperCase() | String::toUpperCase |
| Constructor | () -> new Foo() | Foo::new |
Exam Focus
Revise definitions, diagrams, examples, and short-answer points for Method Reference.
Interview Use
Prepare one clear explanation, one practical example, and one common mistake for this Java topic.
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