Contents - Cultural View

Java syntax 192
Modifiers
• static - Makes the field a static member.
• final - Allows the field to be initialized only once in a constructor.
• transient - Indicates that this field will not be stored during serialization.
• volatile - If a field is declared volatile, it is ensured that all threads see a consistent value for the variable.
• Access modifiers - Identical to those used with classes
Inheritance
Classes in Java may only inherit from one class. A class may derive from any class that is not marked as final.
Inheritance is declared using extends keyword. A class may reference itself using this keyword and its direct
superclass using super keyword.
class Foo {
}
class Foobar extends Foo {
}
If a class does not specify the superclass, it implicitly inherits from java.lang.Object class. Thus all classes in Java
are subclasses of Object class.
Overriding methods
Unlike C++, all non-final methods in Java are virtual and can be overridden by the inheriting classes.
class Operation {
}
public int do() {
}
return 0;
class NewOperation extends Operation {
}
public int do() {
}
Abstract classes
return 1;
Abstract classes are classes that only serve as templates and cannot be instantiated. Otherwise it is just like an
ordinary class.
Only abstract classes are allowed to have abstract methods. Abstract methods do not have any implementation and
must be overridden by a subclass unless it is not abstract itself.
abstract class Mammal {
}
public abstract void walk();
class Human extends Mammal {