1. Web & Systems Developer, 30 credits
Software development, part 2
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2. Selection (if statement)
fals
code
true
selection
if (selection)
expression
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3. Selection (if else statement)
import java.util.Scanner;
public class IfStatement{
public static void main (String [] args) {
Scanner scan = new Scanner (System.in);
double hourlySalary = 100;
int hours;
double payment;
System.out.print ("Enter the weekly hours worked:");
hours = scan.nextInt();
if (hours > 40) {
payment = 40 * hourlySalary + (hours - 40) * (hourlySalary * 1.5); }
else {
payment = hours * hourlySalary;
System.out.println ("Weekly salary:" + payment + ” SEK");
Enter the weekly hours worked:60
Weekly salary: SEK
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4. Selection (if else statement)
import java.util.Scanner;
public class IfStatement2{
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
int score;
int ratings;
System.out.print("Enter your exam result (0 to 100 points):");
score = scan.nextInt();
ratings = score / 10;
if (ratings > 7){
System.out.println("Your rate is: VERY GOOD"); }
else if (ratings < 5){
System.out.println("Your rate is: FAIL");
else{
System.out.println("Your rate is: GOOD");
Enter your exam result (0 to 100 points):65
Your rate is: GOOD
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5. Boolean expressions
A conditional statement often uses one of Java's relational operators, which all return boolean answer (true or false):
== Equal to
!= Not equal
< Less than
> Greater than
<= Less than or equal to
>= Greater than or equal to
Note the difference between "equals" -operator (==) and the assignment operator (=)
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6. Boolska uttryck 56 == 56 true ’a’ == ’a’ ’a’ == ’A’ false ’x’ != ’z’
45 < 80
2 >= 6
2 >= 2
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7. Logical expressions The logical NOT - expression:
!a s true if a is false and false if a is true
The logical AND - expression:
a && b is true if both a and b are true. otherwise false
The logical OR- expression:
a || b is true if a or b or both are true. otherwise false
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8. Operatorer för att öka och minska
The expression:
i++;
is the same as:
i = i + 1;
Expression
num++
++num
num--
--num
Operation
add 1
subtract 1
The term's value
gamla värdet
nya värdet
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9. Operatorer för att öka och minska
public class ÖkaMinska{
public static void main (String[] args){
int a = 5;
int b = 5;
int c = 10;
System.out.println(a++); //5
System.out.println(++b); //6
System.out.println(a); //6
System.out.println(b); //6
System.out.println(c c); //10+12 }
Sista raden i varje beräkningssats har finns där för att visa hur man gör en tom rad vid utskriften av resultatet. 5 6 22
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10. Tilldelningsoperatorer+= -= *= /= %=
Exempel
x += y
x -= y
x *= y
x /= y
x %= y
Motsvarar
x = x + y
x = x - y
x = x * y
x = x / y
x = x % y
Exempel:
int summa = 100;
int vara = 50;
summa = summa + vara; // summa = 150
är samma som:
summa += vara; // summa = 150
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11. Blockstatement Block Guess a number between 1 and 10: 6
import java.util.Scanner;
public class Guess{
public static void main (String [] args) {
Scanner scan = new Scanner (System.in);
int rightNumber = 4;
int guessedNumber;
System.out.print ("Guess a number between 1 and 10:");
guessedNumber = scan.nextInt();
if (rightNumber == guessedNumber)
System.out.println ("GOOD, RIGHT NUMBER !!!");
else {
System.out.println ("Your answer was wrong.");
System.out.println ("The correct number was:" + rightNumber); }
Block
Guess a number between 1 and 10: 6
Your answer was wrong.
The correct number was:4
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12. Nested statements Ange betyg: 10 Du har angivit ett felaktigt värde!
import java.util.Scanner;
public class IfStatement3 {
public static void main (String [] args) {
Scanner scan = new Scanner (System.in);
int result;
System.out.print ("Enter your rate:");
result = scan.nextInt ();
if (result> 0 && result <10) {
if (result> 4 && result <= 7) {
System.out.println ("Result = G"); }
else if (result> 7) {
System.out.println ("Result = VG");
else {
System.out.println ("Result = U");
System.out.println("You have entered an incorrect value!");
    }
Ange betyg: 10
Du har angivit ett felaktigt värde!
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13. Iteration (while statement)
The while statement has the following syntax:
code
true
selection
false
while (selection)
code;
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14. Iteration (while- sats)
import java.util.Scanner;
public class Counter {
public static void main (String [] args) {
Scanner scan = new Scanner (System.in);
int sum = 0;
int number;
int index = 1;
System.out.print ("Enter an integer:");
number = scan.nextInt ();
while (index <= number) {
sum += index; // sum = sum + index
index ++; // index = index + 1; }
System.out.println (" " + number + "=" + sum);
Enter an integer:9
=45
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15. Iteration (for statement)
for (int index = 1; index <= 5; index ++)
sats;
counter
Initialization
Condition
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16. Iteration (for statement)
import java.util.Scanner;
public class Counter {
public static void main (String [] args) {
Scanner scan = new Scanner (System.in);
int sum = 0;
int number;
System.out.print ("Enter an integer:");
number = scan.nextInt ();
for (int index = 1; index <= number; index ++) {
sum = sum + index; }
System.out.println (" " + number + "=" + sum);
Exenpel på en for-sats för att förtydliga föregående OH.
Skriv in ett heltal: 9
=45
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17. Nested statements Total:5 Throw (Yes = 0 No = 1): Total:8 Total:12
import java.util.Random;
import java.util.Scanner;
public class TwentyOne {
public static void main (String [] args) {
Random random = new Random ();
Scanner scan = new Scanner (System.in);
int sum = 0;
int result;
boolean play = true;
while (play) {
sum += random.nextInt (6) + 1;
System.out.println ("Total:" + sum);
if (sum <22) {
System.out.println ("Throw (Yes = 0 No = 1):");
result = scan.nextInt ();
if (result!= 0) {
play = false; }
else {
System.out.println ("Result:" + sum);
Total:5
Throw (Yes = 0 No = 1):
Total:8
Total:12
Total:15 1
Result:15
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