Java-i Lesson3 Op Foc1

8/6/2019 Java-i Lesson3 Op Foc1

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Lesson3: JAVA

INTRODUCTION TO JAVA PROGRAMMING

Operators and Flow of Control


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Relational Operator

The Relational Operators determine therelationship that one operand has to theother.

e.g. Equality and OrderingOperator Result== Equal to

!= Not equal to

> Greater than

< Less than

>= Greater than or equal to


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Boolean Logical Operator

Boolean logical operators operate only on booleanoperands.Operator Result

& Logical AND

| Logical OR^ Logical XOR(exclusive OR)|| Short-Circuit OR&& Short-Circuit AND! Logical Unary NOT== Equal to!= Not Equal to


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Boolean Logical Operator

Logical Operation Effect

A B A|B A&B A^B !A

0 0 0 0 0 11 0 1 0 1 0

0 1 1 0 1 1

1 1 1 1 0 0


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Boolean Logical Operator (Code)

class Logic{public static void main (String Args[]){

boolean a = true;

boolean b = false;

boolean c = a | b;

boolean d = a & b;

boolean e = a ^ b;

boolean f = (!a & b) | (a & !b);

boolean g = !a;

System.out.println(" a=" + a);

System.out.println(" b=" + b);

System.out.println(" a|b=" + c);System.out.println(" a&b=" + d);

System.out.println(" a^b=" + e);

System.out.println(" !a&b|a&!b=" + f);

System.out.println(" !a=" + g);

}

} // Code is From The Complete Reference JAVA 2, Herbert Schildt


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Flow of Control

Sequence

Selection

Iteration


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Sequence

Key points:

order of operations may or may not beimportant

order of evaluation within a singlestatement can be critical

example:a = b++;

a = b = read(input);


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Order of precedence

parentheses before operators

then multiplication and division

then addition and subtraction left to right for equal precedence ops

RHS of an assignment before LHS

if in doubt use brackets use brackets anyway (to clarify to other

readers!)


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Selection

if (condition) {

statement1;

}else {

statement2;

}


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Selection

if (condition){

statement1; condition must

} be of type boolean

else {

statement2;}


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Selection

if (condition) {

statement1;

}else {

statement2;

} else branch is optional


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Selection

if (condition) {

statement1;

}

else {

statement2;

} braces may be

omitted if they onlycontain a single

statement


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Selection

if (condition)

statement;

Brackets around theCondition are

essential


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Selection

if (condition1) {

if (condition2) {

statement1;

}

else {statement2;

}

}

else {statement3;

}

if statements can be

nested indentation ignored by

the compiler but helps

(or can mislead!) humanreaders


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Example conditions

if ((i < j) && (eof != true)) .

if ((i < j) && !eof) .

if ((i < j) && !eof()) .

if ((n = input.read())== 0)

Dont use = when you mean ==


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Example Program

class Larger {public static void main(String[] args)

{int x=20;int y=20;

if(x >= y){if (x==y){System.out.println("x="+x+" and y="+y+ " are Equal");

}else {

System.out.println("Both are unequal");}

System.out.println(x+" is the larger.");}

else {System.out.println(y+" is the larger.");}

}}

l 2


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Example 2class Largest {

public static void main(String[] args){

// Read three integers and print which is the larger.

SimpleInput keyboard = new SimpleInput();

System.out.println("Please type three integers.");

int x = keyboard.nextInt(), y = keyboard.nextInt(), z = keyboard.nextInt();

// A variable to hold the answer.

int largest;

if(x >= y){ // It must be either x or z.

if(x >= z){

largest = x;}

else{

largest = z;

}

}

else{ // It must be either y or z.

if(y >= z){

largest = y;

}

else{

largest = z;

}

}

System.out.println("The largest is: "+largest);

}} // Program Code is courtesy of David J. Barnes.


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Practice Exercise

int month=10;

String season;If (month==12 || month ==1 || month ==2)

season =Winter;

else if(month==3 || month ==4 || month ==5)

season=Spring;else if(month==6 || month ==7 || month ==8)

season=Summer;

else if(month==9 || month ==10 || month ==11)

season=Autumn;elseseason= Bogus Month;

System.out.println(October is in the +season +.);


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Practice Exercise Continue

Write a Java Programme which will tellwhether X (a variable) is Even or Odd.

Write a Java Programme which will specifywhether a birth year was in 1950s, 1960s,1970s, 1980s, 1990s.


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Selection-switch

switch (Condition){

Case 1:Statement1;

Case 2:Statement 2;Break;........

Default:Statement n;Break;

}

Condition should be int,short, byte or a char type

Switch Selection is

replacement of If-else for

multiple selections and for

multiple conditions.


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Selection-switch

switch (Condition){

Case 1:Statement1;

Case 2:Statement 2;break;........

default:Statement n;Break;

}

Break Used to break the

condition

If none of the Case

Statement satisfies

Default condition will

work

This Should be an

Integer or Constant

value

Remember this is

COLON sign notSemiColon or Delimeter


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Example-switch Statement

class switchT{

public static void main(String[] Args){

int x=1;

switch(x){case 1:

System.out.println("Out put is 1: "+x);case 2:

System.out.println("Out put is 2");break;

case 3:System.out.println("Out put is 3");break;

default:

System.out.println("We were expecting X");break;

}}

}


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Practice Switch Statement

int month=10;String season;switch(month){case 12:case 1:case 2:season=Winter;

break;}System.out.println(October is in the + season+.);


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Iteration

while simplest

for most common

do .. While uncommon


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While Statement

while ( condition)

{

body statements;

}

while the conditionevaluates to true,repeatedly loop executingthe body statements

condition is tested

before each passthrough the body

body statements should

have some effect on thecondition or you could

loop indefinitely


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While Statement

int a=10;

while (a > 0) {

System.out.println (a);a = a-1;

}

System.out.println (You Lost The Game");


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Practice While Statement

int a=10;while (a > 0) {

System.out.println (a);

while(a>0 && a


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Practice While Statement

int n=10;

while (n != 1) {

System.out.println (n);

if (n%2 == 0) { // n is even

n = n / 2;

}

else { // n is odd

n = n*3 + 1;

}

}

// Work Out Yourself to find the Output


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do... while Statement

do {

body statements;

}while ( condition);

similar to while statement

BUT condition is tested after

each pass through the body

so body statements will

always be executed at least

once

body statements should

have some effect on the

condition or you could loop

indefinitely


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do...while statement

int a=10;

do{

System.out.println (a);a = a-1;

} while (a > 0);

System.out.println (You Lost The Game");


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for statement

for (initialisation; while condition; end of loop operation) {

body statements;

}

for KeywordVariable Initialisation

Loop Condition

Loop termination Condition


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for statement

most convenient method for

counter based iterations

sequence of execution:

initialisation

is while condition true?

if so, execute body statements execute end of loop operation

is while condition true

etc


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for statement Difference and common features ofwhile and for loop

for (INITIALIZER; CONDITION; INCREMENTOR) {

BODY

}

INITIALIZER;

while (CONDITION) {

BODY

INCREMENTOR

}


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for statement

for (int i=0; i


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for statement

break statement has importance in loop

statements

After reading break statement our compiler

came out of loop and read the next statement

after loop


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Practice for statementint number;

boolean flag = true;

number = 4;

for(int i=2; i


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Nested for Loops Like any other programming Language Java does

allow loops

for(int i=0; i


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Extra Information on for Loops

you can nest loops

you can break execution and jump outside

the loop

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