java-functional-programming

Functional programming is a paradigm that allows programming using expressions i.e. declaring functions, passing functions as arguments and using functions as statements.

Implementations using Structural Programming

• Print each element from list in its own line
• Print courses, courses having name with Spring, courses having name greater than 3 characters
• Print Square of each number in the list
• Print sum of all elements in the list
• Print max and min number from all elements in the list
• Square every number in the list and find the sum of squares
• Cube every number in the list and find the sum of cubes
• Find sum of odd numbers in the list
• Print distinct numbers in the list
• Sort list of numbers and print it
• Sort list of strings and print it
• Square each element of list and collect it as new list
• Find all even element of list and collect it as new list
• Find length of each course element of list and collect it as new list

Implementations using Functional Programming

Using Streams, Filters and Lambdas:

• Print each element from list in its own line
• Print courses, courses having name with Spring, courses having name greater than 3 characters

Using Map:

• Print Square of each number in the list

Using Reduce:

• Print sum of all elements in the list
• Print max and min number from all elements in the list
• Square every number in a list and find the sum of squares
• Cube every number in a list and find the sum of cubes
• Find sum of odd numbers in a list

Using Distinct and Sorted:

• Print distinct numbers in the list
• Sort list of numbers and print it
• Sort list of strings and print it

Using Collect:

• Square each element of list and collect it as new list
• Find all even element of list and collect it as new list
• Find length of each course element of list and collect it as new list

Using allMatch, noneMatch, anyMatch:

• Example

Using Comparator:

• Example

Using skip, limit:

• Example

Using max, min, findFirst, findAny:

• Example

Using sum, average, count:

• Example

Using groupingBy:

• Example

Using Stream.of, Arrays.stream, IntStream, LongStream, BigInteger:

• Example

Using joining, flatMap:

• Example

Using parallelStreams:

• Example

Terminal or Intermediate operations:

• Function or method which returns another stream of element called as Intermediate functions or methods or operations. They are Lazy and execute only when terminal operation is executed.
• Function or method which does not return another stream of element called as Terminal functions or methods or operations.
• Example

Functional Interfaces:

A functional interface has exactly one abstract method.

• Predicate<T>: Represents a predicate (boolean-valued function) of one argument.
  • Example
• Function<T, R>: Represents a function that accepts one argument and produces a result.
  • Example
• Consumer<T>: Represents an operation that accepts a single input argument and returns no result.
  • Example
• BinaryOperator<T>: Represents an operation upon two operands of the same type, producing a result of the same type as the operands.
  • Example
• Supplier<T>: Represents a supplier of results. It does not take any arguments.
  • Example
• UnaryOperatory<T>: Represents an operation on a single operand that produces a result of the same type as its operand.
  • Example
• BiPredicate<T, R>: Represents a predicate (boolean-valued function) of two arguments.
  • Example
• BiFunction<T, U, R>: Represents a function that accepts two arguments and produces a result.
  • Example
• BiConsumer<T, U>: Represents an operation that accepts two input arguments and returns no result.
  • Example
• IntBinaryOperator: Represents an operation upon two int-valued operands and producing an int-valued result.
  • Example
• IntConsumer: Represents an operation that accepts a single int-valued argument and returns no result.
  • Example
• IntFunction<R>: Represents a function that accepts an int-valued argument and produces a result.
  • Example
• IntPredicate: Represents a predicate (boolean-valued function) of one int-valued argument.
  • Example
• IntSupplier: Represents a supplier of int-valued results.
  • Example
• IntToDoubleFunction: Represents a function that accepts an int-valued argument and produces a double-valued result.
  • Example
• IntToLongFunction: Represents a function that accepts an int-valued argument and produces a long-valued result.
  • Example
• IntUnaryOperator: Represents an operation on a single int-valued operand that produces an int-valued result.
  • Example

Behavior Parameterization:

Passing the behaviour as parameter or argument to a method is called as Behavior Parameterization.

• Example

Method Reference:

Method reference is used to refer method of functional interface. The Method reference can only be used to replace a single method of lambda expression.

• Example

Higher Order Functions:

Higher Order Function is a function which returns a function.

• Example

Java Made Easy:

Few examples of real time Java problems that made very easy using functional programming

• Example