Summary 3

• Object methods are called on the object:

  myObject.myMethod();  //correct object method call
  myMethod(myObject);  ////illegal object method call

• Java indexes are zero-based.
• Java strings have a length property which is not zero based; this allows a null string to have a length of 0 (zero).
• The Java escape character is a backslash and is used to instruct the interpreter to interpret the character that follows it literally, or to indicate a special character such as a newline character.
• Classes have a public interface and a hidden implementation.
• Every object that is an instance of a particular class, inherits all the methods and variables of that class.
• The access level public in a class definition means that the class can be instantiated by any other class.

  public class MyClass {
  
  }

• Class constructors must have the same name as the class, and initialise the instance variables of the object they instantiate.
• Class definitions must include definitions of all instance methods.
• The access level public in a method definition means that the method can be called by any other class.

  //public int myMethod() {
  
  }

• Method definitions should include an access level and the data type of the return value.

  //public int myMethod() {
  
  }

• All instance variables must be declared in the class definition, but placed outside the constructor and method definitions.
• Classes are instantiated as follows:

  ClassName objectName = new objectConstructorName(arguments);

• More than one instance of most classes can exist simultaneously, and method calls to the same methods of each object can be made whenever required.  
• The console command javadoc ClassName.java will generate documentation for the class ClassName, provided the class has been commented correctly.
• Comment blocks to be interpreted by javadoc must begin with \**
• The indicator @param must precede a comment line that describes a constructor or method parameter.
• The indicator @return must precede a comment line that describes what a method returns.
• Classes may contain more than one constructor; the constructor arguments will determine which constructor is used for object instantiation.

 © G. Hearn, & University of the Western Cape, 2006