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CSE 142

Lecture Notes

Week 2

Data types

  • Three main data types (you will learn more later)
Data type Description
int integers, pos, zero, neg, up to 2^31-1
double floating point numbers (real), pos, zero, neg, up to 10^308
String text characters
  • Literals
  • int literal: number without a decimal, e.g., -7, 0, 103
  • double literal: number with a decimal, e.g., -7.0, 0.2, 103.5
  • String literal: characters surrounded by quotes, e.g., "hello world"

Variables

  • In Java we need to declare variables with a type and a name before they can be used
  • Once a variable is declared you cannot redeclare it (with a type)

Assignment statements

  • = is the assignment operator, it has nothing to do with equality
  • Assignment statements should be read right-to-left
// 1 is stored in the int variable named x
int x = 1;
// 1 is added to the current value of x (in this case 1), resulting in 2, and that is stored back into x
x = x + 1;

For Loops

  • Structure
for(initialization; test; update) {
    body
}

Constants

  • Should be at the top of your program
  • Start with public static final