Lecture 1 Review of 1301/1321 CSE 1322 4/26/2018
Common data types byte, short, int, long, double, float, char, C#: bool, string /String Java: boolean, String 4/26/2018
To declare a variable <type> <name>; Example: int myNum; You can also initialize it when you declare it: int myNum = 42; double taxRate=.07; float interestRate=.065f; 4/26/2018
C# Console I/O Console.Write(X); Console.WriteLine(X); string A = Console.ReadLine(); Note that ReadLine() returns a string, so if you want to get something else from the user (and int for example), you would have to convert it. int myNum = Int32.Parse(Console.ReadLine()); This takes in input from the user (as a string) and then passes this string to the Parse method of the Int32 class; this Parse method returns an int, so this is a valid assignment since now the left and the right side of the assignment (=) operator are of the same type. 4/26/2018
Java Console I/O System.out.print(x); System.out.println(x); String word=scan.nextLine(); int num=scan.nextInt(); Recall that with using scanner, if you mix the use of nextLine() and nextInt(), etc., you may have to flush the stream. 4/26/2018
Data validity For 1322, you may assume the user will give valid input, as far as the data type. You will have to ensure the data is in the proper range. Later in the course we will explore exception handling. 4/26/2018
Pseudocode – Console input NAME = “” PRINT “What is your name?: ” READ user_input NAME← user_input PRINT Hello +NAME 4/3/2019
C# User interaction Console.Write("What is your name? "); string name = Console.ReadLine(); Console.WriteLine("Hello " + name); Notice in the above that the + operator acts as string concatenation. 4/26/2018
Java User interaction System.out.print(“What is your name? “); String name= scan.nextLine(); System.out.println(“Hello “+name): Notice in the above that the + operator acts as string concatenation. 4/26/2018
Pseudocode - IF Statement Problem Statement: Acquire the user age from the console and use if else statements to make a decision ---------------------------------------------------------------------------------------------------------- AGE ← 0 PRINT “How old are you?: ” READ user_input AGE ← user_input IF (AGE < 18) THEN PRINT “can’t vote or drink” ELSE IF (AGE <21) PRINT “can vote but can’t drink” ELSE PRINT “You can vote and drink, but don't vote shortly after drinking!” ENDIF 4/3/2019
C# Conditionals Console.Write("How old are you? "); int age = Int32.Parse(Console.ReadLine()); if (age < 18) Console.WriteLine("You cannot drink or vote."); else if (age < 21) Console.WriteLine("You can vote but not drink."); else Console.WriteLine("You can vote and drink, but don't vote shortly after drinking!"); 4/26/2018
Java Conditionals System.out.print("How old are you? "); int age = scan.nextInt(); if (age < 18){ System.out.println("You cannot drink or vote."); } else if (age < 21){ System.out.println("You can vote but not drink."); } else { System.out.println("You can vote and drink, but don't vote shortly after drinking!"); } 4/26/2018
Notice in the previous examples that we don't have to use curly-brackets to define the block in the if-else because we only want to control one line of code if you wanted to do more than one statement, use { } to mark the body of the if-else statement blocks. { } 4/26/2018
Declaring Methods You declare a method in java and C# using the following pattern: <return type> <name> (<parameter(s)>) { <body of method> } 4/26/2018
Method Returns The return type of a method indicates the type of value that the method sends back to the calling location. The return statement halts execution within the method and (optionally) returns a value A method that does not return a value has a void return type A return statement specifies the value that will be returned return expression; Its expression must conform to the return type 4/26/2018
Pseudocode – void method menu METHOD PrintMenu BEGIN PRINT "1. Display result" PRINT "2. Add a number" PRINT “3. Delete a number" PRINT "4. QUIT" END PrintMenu 4/3/2019
Method examples 1 a menu C# void PrintMenu() { Console.WriteLine("1. Display result"); Console.WriteLine("2. Add a number"); Console.WriteLine("3. Delete a number"); Console.WriteLine("4. QUIT"); } 4/26/2018
Method examples 1 a menu java void PrintMenu() { System.out.println("1. Display result"); System.out.println("2. Add a number"); System.out.println("3. Delete a number"); System.out.println("4. QUIT"); } 4/26/2018
Pseudocode –method menu with input and return METHOD GetChoice() BEGIN choice ← 0 DO PRINT “Enter your choice (1-4) : “ READ user input choice ← user input WHILE choice is less than 1 or choice is greater than 4 ENDDO return choice; END GetChoice 4/3/2019
Method examples 2 choice java int GetChoice() { int choice; do { System.out.print("Enter your choice (1-4) : "); choice = scan.nextInt(); } while ((choice < 1) || (choice > 4)); return choice; } 4/26/2018
Method examples 2 choice C# int GetChoice() { int choice; do { Console.Write("Enter your choice (1-4) : "); choice = Int32.Parse(Console.ReadLine()); } while ((choice < 1) || (choice > 4)); return choice; } 4/26/2018
Pseudocode –for loop FOR month = 1 to 12 block of statements ENDFOR 4/3/2019
for loops java for(<initialize>; <conditional>; <post-activity>) { <body/work> } int sum=0; for ( int i=0; i < 100; i += 2) { sum+= i; } System.out.println(“the sum is “+sum); 4/26/2018
for loops C# for(<initialize>; <conditional>; <post-activity>) { <body/work> } int sum=0; for ( int i=0; i < 100; i += 2) { sum+= i; } Console.WriteLine(“the sum is “+sum); 4/26/2018
Pseudocode –do while loop REPEAT block of statements UNTIL condition DO WHILE condition ENDDO 4/3/2019
C# do while loop do { <body/work> } while (<conditional>); int i = 10; int total=0; do { total+=i; i--; } while (i > 0); Console.Write(“Total “+total); 4/26/2018
Java do while loop do { <body/work> } while (<conditional>); int i = 10; int total=0; do { total+=i; i--; } while (i > 0); System.out.print(“Total “+total); 4/26/2018
Pseudocode – while loop WHILE condition = true block of statements ENDWHILE 4/3/2019
Java while loop while (<conditional>) { <body/work> } int i = 0; while (i != 0) { i -= 1; } System.out.println(“the result is “+i); 4/26/2018
C# while loop while (<conditional>) { <body/work> } int i = 0; while (i != 0) { i -= 1; } Console.Write(“result is “+i); 4/26/2018