HashCode: Exam questions tests - Sun Certified Java Programmer 310-065 - Lesson 61

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Title: HashCode: Exam questions tests - Sun Certified Java Programmer 310-065 - Lesson 61

Duration:  16 minutes

Summary: In this video, we are continuing the discussion of the first exam set. We start with a question that tests on the use of equals() and hashCode() methods. You need to know that the equals() algorithm must be at least as precise as the hashCode() method. Then, we look at sorting an array of strings using the Comparator class. This class has a method named ‘compare()’. As the name implies, this method compares two objects to determine which one comes before the other. The array elements were compared using the second character of the word. In the question before last we look at a TreeSet. No matter how the elements are added to the TreeSet, they are sorted. In the final question, we discuss working with a HashMap. We have a method that mangles the elements in the map, and returns the value before the key. When we try to retrieve the elements one of them would return the correct value and the other would return null.

Methodology of the development of example: Good coding standard and simplified design to prepare for the Java programmer certification exam CX-310-065.

Technology Used: Java – Core Concepts.

Keywords: Class, object, hashCode, equals, length(), Comparator, compare(), TreeSet, Integer, HashMap.