Day 4 of 100 - Java: Data Types

Binge watching, Java Basics

String concatenation:

today = 4;
total = 100;
System.out.println("Day "+today+" of "+total+" - Learning Java");

Points:

1. Use lower camel case for variable names.
2. use full names. speed instead of sp;
3. Start variable with a letter. var8 or v1 and not 8var
4. Long or Integer for integer values. Double for fractions

5. String or Character datatypes. Character cannot be used for calculations
   

   String text = "(a) Today is January 12 2022";
   char hello = '4';
   char three = '3';
   //char ten = '10'; // Cannot store more than one letter.
   

6. boolean
   

   //boolean hello = 21; //incorrect
   boolean hello = true;
   // long number = 100.1; // only natural numbers
   

7. Variable Arithmetic
   

   int negNumber = -20; // =-20
   int multNumber = 5*6; // = 30
   //
   double divide = 5/2; //=2
   double divide2 = 24/5; //not 4.8, =4
   double accurateDivide = 5/2.0; // 2.5
   //
   int x = 2+3; //5
   int y = 4-5; //-1
   int z = x*y; //-5
   //
   double paid = 10;
   double change = 3.25;
   double tip = (paid-change)*0.2;
   // double tip = paid - change * 0.2;
   

8. If in doubt, use parentheses (). * or / before + or -.

9. Casting
   

   double div = 5/2;
   System.out.println(div);//2
   double accurateDiv = (double)x/y;
   System.out.println(accurateDiv);