COMP SCIENCE JAVA MIDTERM REVIEW 2023, Exams of Java Programming

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INTRO. JAVA MIDTERM

REVIEW

(JAVA CRASH COURSE)

Tae Soo Kim

Primitive Types

• Basic types used in Java (DON’T USE AS A VARIABLE NAME) - int, double, float, byte, short, long, char etc..
• Strings do not belong here.

Primitive Types

• int variable = 6;
• int double = 2;
• int _double = 2;
• double fine = 2.0;
• int notFine = 2.0;
• char yes = ‘a’;
• char nooo = ‘abc’;
• char hmm = “a”

Variables

• 3 parts
  • Type name = value;
• Declaration vs. Assignment
  • int declarationOfInt; //declaration
  • String declarationOfString; //declaration
  • declarationOfInt = 200; //assignment of value 200
  • declarationOfString = “acethemidterm”; //assignment
• Declaration and assignment simultaneously
  • String doItAll = “atonce”;

Arithmetic

• Two things: order of operation and return types
  • Order of operation:
    • 𝑥 = −𝑏±^ 2𝑎𝑏^2 −4𝑎𝑐in Java..

Arithmetic

• Some useful insights

Arithmetic

• Modular arithmetic
  • Useful for even/odd computations, execution per n iterations
  • Even numbers = (x % 2) == 0;
  • Odd numbers = (x % 2) == 1;
  • -8 % 5 => -

Arithmetic

• Var++ vs. ++Var

Inputs

• Scanner class is your best friend.
  • Be sure to import java.util.Scanner;
  • Declare/Initialize Scanner object
    • Scanner whateverName = new Scanner(System.in);
  • whateverName.next() - a String word (read until next white space)
  • whateverName.nextInt() – a int number
  • whateverName.nextLine() – a String line (read until user presses enter, ie. \n)

Inputs

Need this to use line 9

More generally, IOException

Strings

• “ m i d t e r m ”
• 0 1 2 3 4 5 6 <- indices
• “midterm”.indexOf(‘d’) => 2
• “midterm”.indexOf(“d”) => 2
• “midterm”.indexOf(“dte”) => 2
• “midterm”.indexOf(“erm”) => 4
• “midterm”.indexOf(‘m’) => 0
• “midterm”.indexOf(“ermm”) => -
• “midterm”.substring(1).indexOf(“m”) => ??

Strings

• “ m i d t e r m ”
• 0 1 2 3 4 5 6 <- indices
• “midterm”.indexOf(‘d’) => 2
• “midterm”.indexOf(“d”) => 2
• “midterm”.indexOf(“dte”) => 2
• “midterm”.indexOf(“erm”) => 4
• “midterm”.indexOf(‘m’) => 0
• “midterm”.indexOf(“ermm”) => -
• “midterm”.substring(1).indexOf(“m”) => 5
  • “midterm”.substring(1) => “idterm”
  • “idterm”.indexOf(“m”) => 5

Decisions

If ( BOOLEAN STATEMENT) { code } else { code }

Tough Decisions