Overview and example code of method references and construction references in Java8
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I. Overview of method references
A method reference is an abbreviation for a specific Lamda expression. The idea is to call the function directly using the method name if you can replace the Lamda expression. Its syntax format: class name:: method name.
Two and three methods are quoted.
1 A reference to a static method
Syntax format: static class name (ClassName):: method name (MethodName)
Example:
/ / 1 Lamda static method @ Test public void LamdaSTest () {String youku1327 = "1327"; Function function = s-> ObjectUtils.allNotNull (youku1327); System.out.println (function.apply (youku1327)); / / true} / / static method reference @ Test public void MethodRefTest () {String youku1327 = "youku1327"; Function function = ObjectUtils::allNotNull; System.out.println (function.apply (youku1327)); / / true}
2 references to methods that point to the object instance
Syntax format: instance name (instanceName):: method name (MethodName)
This object refers to an external object that is not an input parameter
Example:
/ / 2 Lamda expression @ Test public void ObjectLamdaTest () {Car car = new Car, "black", "China", 20); Supplier supplier = ()-> car.getColor (); System.out.println (supplier.get ()); / / black} / / object reference @ Test public void ObjectRefTest () {Car car = new Car ("100s", "black", "China", 20); Supplier supplier = car::getColor; System.out.println (supplier.get ()) / / black}
3 method reference pointing to the instance
Syntax format: object name (ClassName):: method name (Method) this object refers to the input parameter object
/ / 3 Lamda expression @ Test public void InstanceMethodLamdaTest () {Car car = new Car ("100s", "black", "China", 20); Function function = s-> s.getColor (); System.out.println (function.apply (car)); / / black} @ Test public void InstanceMethodRefTest () {Car car = new Car ("100s", "black", "China", 20); Function function = Car::getColor; System.out.println (function.apply (car)); / / black}
III. Constructor reference
Syntax format: object name (ClassName):: new
@ Test public void constructLamdaTest () {BiFunction biFunction = (youku1327 aDouble)-> new Car; Car car = biFunction.apply ("youku1327", 50.0); / / Car (code=youku1327, color=null, factory=null, price=50.0) System.out.println (car);} @ Test public void construcMethodRefTest () {BiFunction biFunction = Car::new; Car car = biFunction.apply ("youku1327", 50.0); / / Car (code=youku1327, color=null, factory=null, price=50.0) System.out.println (car);}
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