Review Session Jai Madhok

 Identifiers- What are they?  Rules to determine invalid Vs valid identifiers - Cannot be a reserved word - No spaces in between - No Symbols other than the ‘$’ and ‘_’ - Cannot begin with a digit

 3 kinds of primitive data types  Type conversion between data types - Implicit Vs Explicit type conversion  The ‘Cast’ operator: Syntax: (dataType) Expression  What happens when an operator has mixed operands?

It is an ‘Object’ In Java, they are enclosed in double quotes What is a null string? Empty string? How does indexing work? Predefined Methods: - substring(startIndex, stopIndex) - charAt(index) - indexOf(ch) - concat() - length() - replace() - toLowerCase()/toUpperCase()

Use the word final Identifier is in all Capital Letters Memory location whose content is not allowed to change during program execution Ex: final int CENTS_PER_DOLLAR=100; Several Advantages: - Prevent typographical errors - Easy to modify the program in the future - If you mistype the name of the location computer will warn you as compared to typing in a wrong value which the computer will blindly accept - Good programming practice

To put data into variables from an input device we first create an input stream object and associate it with a standard input device Scanner scan= new Scanner (System.in) More about Scanner: - next() - nextInt() - nextDouble() - nextLine() How do we read in a single character using a scanner object? Know how to use these!

Sometimes we read in input in the form of a string and then want to extract numeric data from it How do we do this? Tokenize and Parse Syntax: StringTokenizer t= new StringTokenizer(str, delimiters) Say we want an integer: int a= Integer.parseInt(t.nextToken()) Other method: Double.parseDouble() Note: Parsing and type casting are different things

A file is defined as an area in secondary storage used to hold information Scanner scanf= new Scanner(new FileReader(filename1)); PrintWriter oFile= new PrintWriter(filename2); Warning: Closing the file you are writing to is more important than you think it is Use same methods for reading and writing/formatting files as you have been for user input/monitor display

Syntax: System.out.printf(formatString, argumentList) formatString: is a string specifying the format argumentList: list of arguments containing constant values, variables, expressions separated by commas Example: System.out.printf(“There are %.2f inches in %d centimeters %n”,cm/2.54, cm) Where cm is a variable of the type int. Note: You can also use the DecimalFormat class to format your decimal output. Take your pick!

compareTo Compare Strings character by character until a mismatch is found. What does this method return? What is the basis for deciding what a mismatch is and what it isn’t?equals Case sensitive method How to solve the case sensitivity issue? What does the method return?

(). [] Unary Operators: negation, casting, not (!), ++, -- Arithmetic Operators I: * / % Arithmetic Operators II: + - Comparison Operators: >= Equivalence Operators: == != Logical AND: && Logical OR: || Ternary Operator: ?: Assignment Operators: ==, +=, -=, *=, /=, %=

Provide alternatives to sequential program execution and are used to alter flow of execution Alternatives are: (i) Selection – if, if/else, switch/case (ii) Repitition – for, while, do-while

 Using loop control variables - Counter controlled while loops - Sentinel Controlled while loops - Flag controlled while loops  EOF controlled while loops  Do-While Loops  different from a generic while T F

for (initial statement; loop condition; update Statement) KNOW THIS LOOP COLD! Initial Statement Loop Condition Statements Update Statement T F

 Exit early from a loop  Skip the remaining cases in a switch case construct  Don’t try and use them at random places to make your code work, most of the time it won’t.

 util – Scanner, StringTokenizer  io- BufferedReader, FileReader  text- DecimalFormat  lang – String, Math

 Reading flow in java: a = a + 2;  ‘A’ in ASCII is 65  ASCII is a subset of Unicode  Escape Sequences  Compound Operators  Increment/Decrement operators, pre/post

Read up some common methods of the following classes for use in the assignments and exams. - String - Scanner - StringTokenizer - Math - Character

 True/False  Multiple Choice  Code Tracing  Code Completion  Finding Errors  Other random kinds of questions like matching exercises are a possibility

Read through all questions carefully Write answers legibly, because we have to be able to read them to grade them Show all work for partial credit Do not spend too much time on any one particular problem if it is causing trouble, come back to it later on Read through the chapter summaries in the text book and all of Dr.H’s class notes Good Luck!

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char let =‘A’; for (int i=1; i<=3;i++) { for(int j=I;j<5;j++) System.out.print(let); System.out.println(); let+=1; } Predict the output? [6 points] Difficulty: Medium

n1= 6; n2=10; if(n1 >= n2/2) { if(true && false) System.out.print(“ one “); } else System.out.print(“two “ ); System.out.print(“three ”); Predict the output? [3 points] Difficulty: Easy

int num=6; while(num<16) { switch(num%4) { case 1: System.out.println(“one”); break; case 2: System.out.println(“two”); case 3: System.out.println(“three”);break; case 0: System.out.println(“multiple”); } num+=3; } [4-6 points] Difficulty: Medium

boolean a=true, b=false; if (a && (true|| !b) ) if( b || (!a && false) ) System.out.println(‘’happy”); else System.out.println(“ halloween” ); System.out.println(“goblins”); [6 points]Difficulty: Medium