Java-Concepts-Java-Basics Seminar

[born_for seminars]

Basic Java Syntax and Semantics
Methods, Messages, and Signatures
Classes implement methods, and objects are instances of classes.
Objects that share common behavior are grouped into classes.
An object responds to a message only if its class implements a corresponding method.
To correspond the method must have the same name as the message.
Messages are sometimes accompanied by parameters and sometimes not:
pen.move(); // No parameter expected
pen.moveDown(8); // One parameter expected

Basic Java Syntax and Semantics
Some methods return a value and others do not.
To use a method successfully we must know:
What type of value it returns
It’s name (identifier)
The number and type of the parameters it expects
This information is called the method’s signature.
Basic Java Syntax and Semantics
Programming Protocols: Use camelCase

When forming a compound variable name, programmers usually capitalize the first letter of each word except the first.
(For example: taxableIncome)

All the words in a program’s name typically begin with a capital letter (ComputeEmployeePayroll).

Constant names usually are all uppercase (TAX_RATE).
Comments
Comments are explanatory sentences inserted in a program in such a matter that the compiler ignores them.
There are two styles for indicating comments:
End of line comments:
These include all of the text following a double slash (//) on any given line; in other words, this style is best for just one line of comments
Multiline comments:
These include all of the text between an opening /* and a closing */
Additional Operators
Extended Assignment Operators
The assignment operator can be combined with the arithmetic and concatenation operators to provide extended assignment operators. For example:
int a = 17;
String s = "hi";
a += 3; // Equivalent to a = a + 3;
a -= 3; // Equivalent to a = a – 3;
a *= 3; // Equivalent to a = a * 3;
a /= 3; // Equivalent to a = a / 3;
a %= 3; // Equivalent to a = a % 3;
s += " there"; // Equivalent to s = s + “ there”;
Additional Operators
Increment and Decrement
Java includes increment (++) and decrement (--) operators that increase or decrease a variables value by one:
int m = 7;
double x = 6.4;
m++; // Equivalent to m = m + 1;
x--; // Equivalent to x = x – 1.0;
The precedence of the increment and decrement operators is the same as unary plus, unary minus, and cast.
Standard Classes and Methods
Eight methods in the Math Class
Standard Classes and Methods
Using the Math class

double absNum, powerNum, randomNum;

absNum = Math.abs(-30);
powerNum = Math.pow(-3, 3);
randomNum = Math.random();

Results:
absNum = 30 //Absolute value of -30
powerNum = -27 //-3 to the 2nd power
randomNum = ????? //Random number between 0 and 1