Download java - fundamental summary

Grade 10 IT – summary of fundamental programming skills
Description
Java code
Declare string
String name;
Enter a string
name = JOptionPane.showInputdialog(“Enter your name”);
Declare string AND
String name = JOptionPane.showInputdialog(“Enter your name”);
enter
Display string
System.out.println( name);
JOptionPane.showMessageDialog(null, name);
Display string with
System.out.println( “Name: “+name);
message before
JOptionPane.showMessageDialog(null, “Name: “+name);
Display string in
System.out.println( “We welcome “+name+” to our shop.”);
between the message JOptionPane.showMessageDialog(null, “We welcome “+name+” to our shop.”);
Declare integer
int number1;
Enter integer
String num1 = JOptionPane.showInputdialog(“Enter number 1”);
Change to an integer
number1 = Integer.parseInt(num1);
OR do it all in one
int number1 = Integer.parseInt(JOptionPane.showInputdialog(“Enter number 1”));
int number2 = Integer.parseInt(JOptionPane.showInputdialog(“Enter number 2”));
Declare a real number double number3;
Enter the real number String num3 = JOptionPane.showInputdialog(“Enter number 3”);
Change to a real
number3 = Double.parseDouble(num3);
number
OR do it all in one
double number3 = Double.parseDouble (JOptionPane.showInputdialog(“Enter number 3”));
double number4 = Double.parseDouble (JOptionPane.showInputdialog(“Enter number 4”));
Add integers
System.out.println(number1+” plus “+number 2+” is “+(number1+number2));
int answer1 = number1+number2;
System.out.println(number1+” plus “+number 2+” is “+answer1);
Add real numbers
System.out.println(number3+” plus “+number 4+” is “+(number3+number4));
double answer2 = number3+number4;
System.out.println(number3+” plus “+number 4+” is “+answer2);
Subtract integers
System.out.println(number1+” minus “+number 2+” is “+(number1-number2));
int answer1 = number1-number2;
System.out.println(number1+” minus “+number 2+” is “+answer1);
Subtract real numbers System.out.println(number3+” minus “+number 4+” is “+(number3-number4));
double answer2 = number3-number4;
System.out.println(number3+” minus “+number 4+” is “+answer2);
Multiply integers
System.out.println(number1+” times “+number 2+” is “+(number1*number2));
int answer1 = number1*number2;
System.out.println(number1+” times “+number 2+” is “+answer1);
Multiply real numbers System.out.println(number3+” times “+number 4+” is “+(number3*number4));
double answer2 = number3*number4;
System.out.println(number3+” times “+number 4+” is “+answer2);
Divide integers
System.out.println(number1+” divide by “+number 2+” is “+(number1/number2));
int answer1 = number1/number2;
System.out.println(number1+” divide by “+number 2+” is “+answer1);
Divide real numbers
System.out.println(number3+” divide by “+number 4+” is “+(number3/number4));
double answer2 = number3/number4;
System.out.println(number3+” divide by “+number 4+” is “+answer2);
NB: Integer divide by integer is always an integer AND decimal is truncated (i.e. cut off). If you wanted 5/2 to give
an answer of 2.5 (and not 2) then you have to make the numerator a real number, i.e. 5.0/2
To get the remainder
System.out.println(number1+” divide by “+number 2+” is “+(number1/number2) +
of an integer division
“ with a remainder of “+(number1%number2) );
int answer1 = number1/number2;
int remainder = number1%number2;
System.out.println(number1+” divide by “+number 2+” is “+answer1+
“ with a remainder of “+ remainder );
Declare character
Enter character
Change to a character
OR do it all in one
Count the number of
letters in a string
char letter;
String str = JOptionPane.showInputdialog(“Enter a letter”);
letter = str.charAt(0);
char letter = JOptionPane.showInputdialog(“Enter a letter”).charAt(0);
String word = JOptionPane.showInputdialog(“Enter a word”);
int count = word.length();
JOptionPane.showMessageDialog(null, “There are “+count+” letters in the word.”);
Typecasting
String to ...
... to String
Real number to integer
(NB: will be truncated,
e.g. 5.5 becomes 5)
Integer to real number
(NB: only a decimal is
added on,
e.g. 5 becomes 5.0)
Character to integer
(to show its ordinal value
 value based on the
ASCII table)
Integer to Character
(to show character based
on the value in the ASCII
table)
To divide two integers
Done when showed how to input the various data types using JOptionPane.
String str = “”+variable;
double num1 = Double.parseDouble
(JOptionPane.showInputdialog(“Enter a real number”));
int num2 = (int) num1;
JOptionPane.showMessageDialog(null, num1+” changes to “+num2);
int num1 = Integer.parseInt(JOptionPane.showInputdialog(“Enter an integer”));
double num2 = (double ) num1;
JOptionPane.showMessageDialog(null, num1+” changes to “+num2);
char letter = JOptionPane.showInputdialog(“Enter a letter”).charAt(0);
int value = (int) letter;
JOptionPane.showMessageDialog(null, letter +” has a value of “+value);
int value = Integer.parseInt
(JOptionPane.showInputdialog(“Enter an integer”));
char letter = (char) value;
JOptionPane.showMessageDialog(null, value +” refers to the character “+letter+
“ in the ASCII table”);
int num1 = Integer.parseInt(JOptionPane.showInputdialog(“Enter an integer”));
int num2 = Integer.parseInt(JOptionPane.showInputdialog(“Enter an integer”));
double answ = num1/num2;
JOptionPane.showMessageDialog(null,num1+” divided by “+num2+” is “+answ);
This will show a truncated integer!!
int num1 = Integer.parseInt(JOptionPane.showInputdialog(“Enter an integer”));
int num2 = Integer.parseInt(JOptionPane.showInputdialog(“Enter an integer”));
double answ = (double) num1/num2;
JOptionPane.showMessageDialog(null,num1+” divided by “+num2+” is “+answ);
This will show a real number!!
int num1 = Integer.parseInt(JOptionPane.showInputdialog(“Enter an integer”));
int num2 = Integer.parseInt(JOptionPane.showInputdialog(“Enter an integer”));
double answ = 1.0* num1/num2;
JOptionPane.showMessageDialog(null,num1+” divided by “+num2+” is “+answ);
This will show a real number!!