csc101_l2 - basic java

8/9/2019 CSC101_L2 - Basic Java

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LECTURE 2

BASIC ELEMENTS OF JAVA


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programming

process of planning and creating a program

computer program

a sequence of statements intended to accomplish a task

programming language

a set of rules, symbols, and special words used to construct pr


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A Java Program

//********************************************************

// This is a simple Java program. It displays three lines

// of text, including the sum of two numbers.

//********************************************************

public class ASimpleJavaProgram

{

public static void main(String[] args)

{

System.out.println("My first Java program.");

System.out.println("The sum of 2 and 3 = " + 5);

System.out.println("7 + 8 = " + (7 + 8));

}

}


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Basics

syntax rules

tell you which statements (instructions) are legal, or acceptedprogramming language, and which are not

a violation of the syntax, or grammatical rules, of a natural lanprogramming language

semantic rules

determine the meaning of the instructions

a violation of the rules of meaning of a natural language or aprogramming language


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Basics

1. Comment

Single-line: //

Multiple-line: /* and */

2. Special Symbols

considered a single symbol

3. Reserved Words (Keyword

int, float, do

char, void, pu

static, throws

letters in a reserved

always lowercase

considered a single


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Basics

4. Identifiers

names of things, such as variables, constants, and methods, that appear in p

consists of letters, digits, the underscore character (_), and the dollar sign ($

begin with a letter, underscore, or the dollar sign

can be made of only letters, digits, the underscore character (_), and the do

other symbols are permitted to form an identifier

Ex:

Note: Java is case sensitive

side Length sideLength

angle! angle

a+b ab

2nd nd


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Data Types

set of values together with a set of operations on tho

Primitive Data Types

fundamental data types in Java

three categories

1. integral2. floating-point

3. boolean


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Arithmetic Operators and Operator Prece

Java has 5 arithmetic operators:

1. addition +

2. subtraction

3. multiplication *

4. division /

5. mod (modulus or remainder) %


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Ex:

2 + 1 * 3

2, 1, 3 - operands

+,* - operators

Unary operator

an operator that has on

operand.

Ex: - 7

Binary operator an operator that has tw

Ex: 7+8


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Order of Precedence

*, /, % (higher)

+, - (lower)

Ex:

Evaluate 3 * 7 - 6 + 2

Answer: 23


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Expressions

integral expression

floating-point or decimal expression

mixed expression


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Two rules apply when evaluating a mixed expression

1. When evaluating an operator in a mixed expression:

If the operator has the same types of operands (that is, both are integer

floating-point numbers), the operator is evaluated according to the type

If the operator has both types of operands (that is, one is an integer and

floating-point number), during calculation the integer is treated tempora

floating-point number with the decimal part of zero, and then the operaThe result is a floating-point number.

2. The entire expression is evaluated according to the prec

rules.


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Evaluate the following expressions.

a. 13 / 4

b. 2 + 12 / 4

c. 21 % 5

d. 3 - 5 % 7

e. 17.0 / 4

f. 8 - 5 * 2.0

g. 14 + 5 % 2 3

h. 15.0 + 3.0 / 2.0


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Evaluate the following expressions.

a. 13 / 4 = 3

b. 2 + 12 / 4 = 5

c. 21 % 5 = 1

d. 3 - 5 % 7 = -2

e. 17.0 / 4 = 4.25

f. 8 - 5 * 2.0 = -2.0

g. 14 + 5 % 2 3 = 12

h. 15.0 + 3.0 / 2.0 = 16.5


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Type Conversion (Casting)

(dataTypeName) expression


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Class StringStrings

data values that contain more than one charactera sequence of zero or more characters

enclosed in double quotation marks (not in single quotati

as are the char data types)


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String and the operator +

the operator +used to concatenate (or join) two strings as well as a string and a numeric va

character.

Ex:

"Sunny" + " Day" evaluates to Sunny Day

"Amount Due = $" + 576.35 evaluates to "Amount $576.35"

"The sum = " + 12 + 26 evaluates to "The sum =

"The sum = " + (12 + 26) evaluates to "The sum


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Increment and Decrement

Ex:

x = 7;

y = ++x;

x = 7;

y = x++;


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Packages, Classes, Methods

package

a collection of related classes

class

used to create Java programs, either application or applet

used to group a set of related operations

used to allow users to create their own data types

method

set of instructions designed to accomplish a specific task


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Ex:

class Math

in java.lang package

abs, cos, exp, max, atan, sqrt,

etc

class Scanner in java.util package

next, nextInt, nextDouble,

useDelimiter

Importing

import packageN

import java.util

import java.util


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Creating Java Application

syntax of a class to create a Java application program

csc101_l2 - basic java

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