Lambdas and Functional Interfaces in Java

@FunctionalInterface public interface Supplier<T> { /** * Gets a result. * * @return a result */ T get(); } class Test { public static void main(String[] args) { Supplier<String> supplier = () -> “Java”; System.out.println(supplier.get()); } } Output: Java class User { private String name; private String username; private String membershipType; private String address; public…

@FunctionalInterface public interface BinaryOperator<T> extends BiFunction<T,T,T> { /** * Returns a {@link BinaryOperator} which returns the lesser of two elements * according to the specified {@code Comparator}. * * @param <T> the type of the input arguments of the comparator * @param comparator a {@code Comparator} for comparing the two values * @return a {@code…

@FunctionalInterface public interface UnaryOperator<T> extends Function<T, T> { /** * Returns a unary operator that always returns its input argument. * * @param <T> the type of the input and output of the operator * @return a unary operator that always returns its input argument */ static <T> UnaryOperator<T> identity() { return t -> t;…

@FunctionalInterface public interface BiFunction<T, U, R> { /** * Applies this function to the given arguments. * * @param t the first function argument * @param u the second function argument * @return the function result */ R apply(T t, U u); /** * Returns a composed function that first applies this function to *…

@FunctionalInterface public interface Function<T, R> { /** * Applies this function to the given argument. * * @param t the function argument * @return the function result */ R apply(T t); /** * Returns a composed function that first applies the {@code before} * function to its input, and then applies this function to the…

@FunctionalInterface public interface BiPredicate<T, U> { /** * Evaluates this predicate on the given arguments. * * @param t the first input argument * @param u the second input argument * @return {@code true} if the input arguments match the predicate, * otherwise {@code false} */ boolean test(T t, U u); /** * Returns a…

@FunctionalInterface public interface Predicate<T> { /** * Evaluates this predicate on the given argument. * * @param t the input argument * @return {@code true} if the input argument matches the predicate, * otherwise {@code false} */ boolean test(T t); /** * Returns a composed predicate that represents a short-circuiting logical * AND of this…

@FunctionalInterface public interface BiConsumer<T, U> { /** * Performs this operation on the given arguments. * * @param t the first input argument * @param u the second input argument */ void accept(T t, U u); /** * Returns a composed {@code BiConsumer} that performs, in sequence, this * operation followed by the {@code after}…

@FunctionalInterface public interface Consumer<T> { /** * Performs this operation on the given argument. * * @param t the input argument */ void accept(T t); /** * Returns a composed {@code Consumer} that performs, in sequence, this * operation followed by the {@code after} operation. If performing either * operation throws an exception, it is…

@FunctionalInterface public interface Runnable { public abstract void run(); } @FunctionalInterface interface MyFunctionalInterface { int printNumbers(int number1, int number2); // we don’t need to put abstract keyword default void printText(String text) { System.out.println(text); } static void printText(String text, boolean enabled) { if (enabled) { System.out.println(text); } else { System.out.println(“Not enabled.”); } } } @FunctionalInterface interface…

@FunctionalInterface interface Signable { void signDocument(); } @FunctionalInterface interface Signable { void signDocument(); } class Test { public static void main(String[] args) { Signable signable = new Signable() { // anonymous class @Override public void signDocument() { System.out.println(“Signing the document…”); } }; signable.signDocument(); } } Output: Signing the document…   Ok, now let’s replace the…