CS100J Spring 2001
Prelim 1 Topics

Overall Prelim 1
+ mostly Java
+ closed book
+ about 4 problems
+ short answer, fill-in-the blank, fill-in-the box
+ font notation: code elements/statements represented with either 
  boldface, fixed-width font (pretty) or $stuff$ (text)
+ covers all lectures and lecture notes, readings, exercises, projects

Problems
+ develop algorithm
+ instructions to someone/something to solve a problem
+ be detailed and descriptive
+ break big problems into smaller ones

Languages
+ programming: automating problem solving
+ building a computer language
  - characters (ASCII, Unicode)
  - words (tokens)
  - sentences (statements)
+ using grammar (syntax) and meaning (semantics) to build statements
+ examples of languages: Java, MATLAB (Matrix Laboratory)
+ Java language elements:
  characters, white space, comments, identifiers, operators, literals,
  punctuation, strings keywords,

Environments
+ MATLAB (running an M-File)
+ Java IDEs (understanding difference between .java and .class)

Output
+ can print directly with $System.out.println(expressionstatement)$
+ can add strings and expressions inside $System.out.println$
  - strings: "stuff"
  - adding: literals + Strings (any combination)
  - leave spaces by adding $" "$
  - escape characters: like $\n$, as in $System.out.print("Hello\n");$
    prints a new line after printing Hello
  - avoid word wrap by adding expressions and strings on different lines

Input
+ using TokenReader and/or BufferedReader for input
  (basically, we give you the code and you use it)
+ boils down to:
  SomethingReader in$ = new SomethingReader(Something);
  int value = in.readInt();       // input integer and store in $value$
  double thing = in.readDouble(); // input double and store in $thing$
  String stuff = in.readString(); // input String and store in $stuff$
+ prompting:
  - print message to user that tells her/him to enter a number
  - does NOT include the actual statement for getting input
  - just the print statement

Empty statement
+ use a sole semicolon ($;$)

Block statement
+ group statements together with ${ s1;s2;...;sn; }$

Expression statements
+ combine literals and other elements with operators
  - operators: + (add), - (subtract), * (multiply), / (divide), % (remainder)
  - literals: integers (whole numbers), doubles (decimal and exponential 
    notation), characters (use ''), booleans ($true$ and $false$)
+ follow precendence and associativity rules!
  - add and divide come first for precedence
  - minus is left associative
+ avoid confusion using parentheses $()$
+ remainder operator (showed up briefly)
  if (x % 2 == 0) System.out.println("Even!");
  else  System.out.println("Odd!");
+ cast:
  - syntax: (type) expression
  - convert a type to another type
  - usually for doubles and ints
    System.out.println( (int) 10.2 + 7) outputs 17

Assignment statements
+ declaring, assigning, using
+ variables (identifiers) have no default values (yet)
+ must delcare before use
+ must put the same type of value inside the variable
  (Java is STRONGLY TYPED)
+ use assign operator ($=$) (means "gets")
+ increment variables: var = var + value
+ swapping values (something similar shows up with min/max)
  int a,b,tmp;
  a = 1; b = 2;
  tmp = a;
  a = b;
  b = tmp;  
+ increment operators ++ and --
  - preincrement:  a = ++c
  - postincrement: b = d++
+ random numbers with $Math.round$ (well, not actually an operator!)
+ style: comment major variables

Condition/Selection statements
+ make choices
+ keywords: $if$, $if$-$else$, $if$-$else if$-$else$
+ basic form: $if (c) s$
+ $c$ represents a boolean expression
  - logical values: $true$ and $false$
  - relations: <, <=, >, >=, ==, !=
  - logical operators: && (and), || (or), and ! (not)
+ use sole $if$, as many $else-if$s, and possibly one $else$
+ style: indent code underneath the condition
  - indentation does NOT mean a new statement!
  - an entire $if$ statement ends at the last $;$ 
    (after the last statement in an $else$ or $else-if$, 
    or last statement in $if$ assuming no $else$ or $else-if$)
  - avoid $break$ and $System.exit$
  - comments for multiple lines of code go above the lines
+ Java does selection if the $c$ evalutates to $true$
  otherwise, Java moves to statement after the $if$ statement
+ nested selection: use a selection statement within a selection statement
+ finding min/max values

Repetition statements
+ loops, iteration
+ keywords: $while$,$for$,$do$-$while$
  (for Prelim 1, you may ONLY use $while$)
+ types:
  - definite: known stopping point, usually means giving count check in $while$
    condition. Examples: echoing, pure repeating, sometimes accumulation
  - indefinte: unknown when the loop will stop, could go on forever (infinite
    loop) Examples: accumulation, conditional update
+ processing input pattern:
  - initial/preprocess:   assign variables
                          look for boundary values/initial conditions
			  use comments to explain what they are "so far"
                          get initial input(s)
  - looping/processing:   start with $while(c)$
                          $c$ is boolean expression (see selection statement!)
                          in $c$, check for "evil" input and stopping values
                          in loop body, do count and updates, if necessary
			  (updates mean things like swapping variables and
			   checking for min/max values -- they use $if$s)
			  get next input
  - final/postprocessing: happens after loop
			  use selection statements to report what may have
			  happened in the loop
+ style
  - indent underneath condition
  - avoid $break$ and $System.exit$
  - avoid infinite loops: provide stopping conditions  
  - comments for multiple lines of code go above the lines