Pramoda Sabat's Blog

Java Stream API introduced in Java 8 and use functional way (lambda function f(x) -> y) to process a collection. It operates over a source data and returns a transformed immutable object. It is one of the most frequently asked interview topic. If you're preparing for Java developer roles, make sure to go through the below consolidated and compiled coding question and answers to bookmark and practice.   Q. Convert a collection of string to upper case : List<String> list = Arrays . asList ( "Bob" , "Piter" , "Andi" , "Joy" ); List<String> listUpper = list .stream() .map( String::toUpperCase ) .collect(Collectors. toList ()); System. out .println( "listUpper - " +listUpper); Output: listUpper - [BOB, PITER, ANDI, JOY] Q. Find Max value from a collection of integer : List<Integer> listInt = Arrays . asList ( 4 , 5 , 7 , 3 , 23 , 89 ); Optional<Integer> value = listInt ...

JDK 7 and earlier: Avoid using null check in if statement. Use ternary operator for null/exist check and assign a default value before using. This will make the code clear and more understandable as comparable to using multiple if, else   statements. JDK 8 and above : Java-8 provides improved API to deal with object null check. Use isPresent() function available in Java.util.Optional interface for null check of single object. Ex – Employee employee = new Employee(); employee .setName( "Pramoda" ); // Getting optional value Optional<Employee> optionalEmployee = Optional. ofNullable ( employee ) .map(Root::getEmployee); System. out .println( "Is Employee present : + optionalemployee .isPresent()); Use Java.util.Optional functional interface for object null check and assign default value to avoid null pointer exception. Ex – Employee employee = new Employee(); employee .setNa...