else Java Keyword

The else keyword is always used in association with the if keyword in an if−else statement. The else clause is
optional and is executed if the if condition is false.

Examples

if (condition)
{
<statements>
}
else
{
<statements>
}

Comments

Generalization and Specialization

Generalization creates a concept with a broader scope. Specialization creates a concept with a narrower scope. Reusing the interface! Inheritance: get the interface from the general class. Objects related by inheritance are all of the same type.

Aggregation and Decomposition

Idea: make new objects by combining existing objects. Reusing the implementation! An aggregation consists of a number of (sub-)concepts which collectively is considered a new concept. A decomposition splits a single concept into a number of (sub-)concepts.

The Class Concept

A class is a collection of objects (or values) and a corresponding set of methods. A class encapsulates the data representation and makes data access possible at a higher level of abstraction. Example 1: A set of vehicles with operations for starting, stopping, driving, get km/liter, etc. Example 2: A time interval, start time, end time, duration, overlapping intervals, etc. Example 3: A string, upper case, compare, lower case, etc. str.equals(otherStr) – class/Java style strcmp(str, otherStr) – C style

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