Lambda-expressions-challenges

Java Lambda expressions challenges

/**
 * Challenge 1:
 * Write the following anonymous class as a lambda expression
 */
Runnable runnable = new Runnable() {
    @Override
    public void run() {
        String myString = "Let's split this up into an array";
        String[] parts = myString.split(" ");
        for (String part : parts) {
            System.out.println(part);
        }
    }
};
/**
 * Challenge 2:
 * Write the following method as a lambda expression, Don't worry about assigning it to anything
 */
   public static String everySecondChar(String source) {
    StringBuilder returnVal = new StringBuilder();
    for (int i = 0; i < source.length(); i++) {
        if (i % 2 == 1) {
            returnVal.append(source.charAt(i));
        }
    }
    return returnVal.toString();
}
/**
 * Challenge 3:
 * Right now the function in challenge 2 doesn't do anything.
 * Write the code that will execute the function with an argument of "1234567890"
 */  
/**
 * Challenge 4:
 * Instead of executing this function(challenge 2) directly,
 * Suppose we want to pass it to a method called everySecondCharacter that accept the function as a parameter
 * and executes it with the argument "1234567890"
 * 
 * It should return the result of the function.
 * For bonus points, don't hard code the argument string within the method
 */
/**
 * Challenge 5:
 * Using the bonus version on challenge 4, call the method and print the result returned from the method
 */
/**
 * Challenge 6:
 * Write a lambda expression that maps to the java.util.Supplier interface
 * This lambda sould return the string "I love Java!", assign it to a variable called iLoveJava
 */
/**
 * Challenge 7:
 * The supplier won't do anything until we use it,
 * Use the Supplier(Challenge 6) to assign the string "I love Java!" to a variable called supplierResult,
 * Then print the variable to the console
 */
/**
 * Challenge 8:
 * There are many interfaces in the Java SDK, and sometimes we can use a lambda expression instead of creating
 * an instance that implements the interface we want to use
 * 
 * Given a specific interface, how wan we tell whether we can map a lambda expression to it ?
 * What's the criteria that has to be met ?
 */
 /**
  * Challenge 9:
  * Suppose we have the following list of the top 5 male and female names for 2015,
  * Write code to print the items in the list in sorted order, and with the first letter in each name upper-cased
  * Use Lambda expressions and Stream operations wherever possible
  */
  /**
  * Challenge 10:
  * Instead of printing out the sorted names(challenge 9),
  * Print out how many names start with the letter 'A'
  */