Methods. world.my first method ( ) No variables. While ( wizard.t >= 0 ) wizard.method1. dragon. Methods. dragon.method1 ( ) No variables.

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1 COSC 117 Exam 2 Key Spring 2011 Part 1: Alice Program Traces (10 Points Each) 1. Discuss what the following Alice program does from the point of view of the user, be very explicit. State what the user sees and when. When the world starts the world.my first method event is run. Also, the wingflex, lastwingflex and secondwingflex are all numeric variables in the dragon object and their initial values are all 1. The t variable is a numeric variable in the wizard object and it has an initial value of 5. Solution: 1. The dragon wings turn forward 2. The wizard says The Wing Flex is The dragon wings turn forward 4. The wizard says The Wing Flex is The dragon wings turn forward 6. The wizard says The Wing Flex is The dragon wings turn forward 8. The wizard says The Wing Flex is The dragon wings turn forward world.my first method ( ) dragon While ( wizard.t >= 0 ) wizard.method1 dragon.method1 ( ) wizard 10. The wizard says The Wing Flex is The dragon wings turn forward 12. The wizard says The Wing Flex is 21.0 dragon.secondwingflex set value to dragon.lastwingflex dragon.lastwingflex set value to dragon.wingflex Do together dragon.leftwing turn right 0.25 revolutions dragon.rightwing turn left 0.25 revolutions Do together dragon.rightwing turn right 0.25 revolutions dragon.leftwing turn left 0.25 revolutions dragon.wingflex set value to ( ( dragon.secondwingflex + dragon.lastwingflex ) ) wizard.method1 ( ) dragon.method1 wizard say ( The Wing Flex is joined with ( dragon.wingflex as a string ) ) decrement wizard.t by 1

2 2. Discuss what the following Alice program does from the point of view of the user, be very explicit. State what the user sees and when. When the world starts the world.my first method event is run. Socrates has a local variable t in its method1 with an initial value of 2. When asked for input the user will type in consecutive odd numbers starting with 1. That is, 1, 3, 5, 7, 9,. Solution: 1. User inputs 1, skatergirl says User inputs 5, skatergirl says User inputs 9, skatergirl says skatergirl says Goodbye world.my first method ( ) socrates socrates.method1 x = 2 socrates.method1 ( [123] x) t = 2 skatergirl Loop x times time t set value to ( ( t + ( ask user for a number question = Enter a Number: ) ) ) skatergirl.method1 x = t skatergirl.method1 ( [123] x) x set value to ( ( x * 2 ) ) skatergirl say ( x as a string ) If ( x <= 30 ) Else socrates.method1 x = 2 skatergirl say Goodbye

3 3. Discuss what the following Alice program does from the point of view of the user, be very explicit. State what the user sees and when. When the program starts the user will click on the scorpion 1 time, then the flamingo 2 times, then the scorpion 2 times, then the flamingo 4 times, then the scorpion 3 times, and then the flamingo 2 times. Both the scorpion and the flamingo have a variable called clicks that starts at 0. Solution: 1. scorpion thinks Man is he pink scorpion thinks Man is he pink flamingo thinks There is a bug scorpion thinks Man is he pink scorpion thinks Man is he pink scorpion thinks Man is he pink flamingo thinks There is a bug flamingo thinks There is a bug flamingo thinks There is a bug flamingo thinks There is a bug flamingo thinks There is a bug scorpion thinks Man is he pink flamingo thinks There is a bug flamingo thinks There is a bug.10.0 world Events When the world starts world.my first method When is clicked on flamingo flamingo.method1 Do: When is clicked on scorpion scorpion.method1 Do: world.my first method ( ) Do Nothing world.method1 ( [123] x) Do: If ( ( ( scorpion.clicks - flamingo.clicks ) ) > 0 ) Else world.t set value to ( ( ( ( scorpion.clicks - flamingo.clicks ) ) + x ) ) world.t set value to ( ( ( ( flamingo.clicks - scorpion.clicks ) ) + x ) ) If ( flamingo.clicks > scorpion.clicks ) Else scorpion flamingo think ( There is a bug. joined with ( world.t as a string ) ) scorpion think ( Man he is pink. joined with ( world.t as a string ) ) scorpion.method1 ( ) flamingo increment scorpion.clicks by 1 world.method1 x = scorpion.clicks flamingo.method1 ( ) increment flamingo.clicks by 1 world.method1 x = flamingo.clicks

4 Part 2: Java Program Traces (15 Points Each) 1. For each of the inputs below give the output of this program. import java.util.scanner; public class Exam2Trace1 { public static int DoSomething(int r, int q) { int x = 1; while (r > 0){ x *= r; r -= q; return x; Scanner keyboard = new Scanner(System.in); int x = keyboard.nextint(); int y = keyboard.nextint(); System.out.println(DoSomething(x, y)); (a) (b) (c) (d) (e) 2 3 3

5 2. For each of the inputs below give the output of this program. import java.util.scanner; public class Exam2Trace2 { public static double DoSomethingElse(int r) { return r*r/2; public static double DoSomething(String r, boolean w) { int a = 0; for (int i = 0; i < r.length(); i++){ char c = r.charat(i); if (w){ if (c == 'a' c == 'e' c == 'i' c == 'o' c == 'u') else if (c!= ' ') return DoSomethingElse(a); Scanner keyboard = new Scanner(System.in); String x = keyboard.nextline(); boolean y = keyboard.nextboolean(); System.out.println(DoSomething(x, y)); (a) This is a test true 8.0 (b) This is a test false 60.0 (c) big deal false 24.0 (d) BIG DEAL true 0.0 (e) BiG deal true 2.0

6 Part 3: Coding (15 Points Each) 1. Write a program that will take in four decimal numbers from the user. The program should print out the sum, product and average of the numbers. All input and output must be done in the main. The sum, product and average must each be calculated using their own methods. import java.util.scanner; public class Exam2Program4 { public static double sum(double n1, double n2, double n3, double n4) { return n1+n2+n3+n4; public static double product(double n1, double n2, double n3, double n4) { return n1*n2*n3*n4; public static double average(double n1, double n2, double n3, double n4) { return (n1+n2+n3+n4)/4; Scanner keyboard = new Scanner(System.in); double n1 = keyboard.nextdouble(); double n2 = keyboard.nextdouble(); double n3 = keyboard.nextdouble(); double n4 = keyboard.nextdouble(); System.out.println("Sum = " + sum(n1, n2, n3, n4)); System.out.println("Product = " + product(n1, n2, n3, n4)); System.out.println("Average = " + average(n1, n2, n3, n4));

7 2. Write a program that will generate 10 random decimal numbers between 5 and 15. The program should print out the largest and smallest of these numbers. You must use the Math.random() command to generate the random numbers. All output must be done in the main. The determination of minimums and maximums must be done using the methods min and max that will take in two decimal numbers and return the minimum and maximum of the numbers respectively. In the min and max methods you may not use Math.min or Math.max functions. public class Exam2Program5 { public static double min(double x, double y) { if (x > y) return y; else return x; public static double max(double x, double y) { if (x < y) return y; else return x; double min = 20; double max = 0; for (int i = 0; i < 10; i++){ double rnd = 10*Math.random()+5; if (rnd < min) min = rnd; if (rnd > max) max = rnd; System.out.println("Min = " + min); System.out.println("Max = " + max);

8 3. Write a program that will take in an entire line as a string and count the number of characters, words and sentences and output these three numbers to the screen. Each of these three counts must be done in their own methods and output to the screen must be done only in the main. You may assume that the line of text has only alphabetic characters, spaces and periods. No numbers, non-period punctuation, or special symbols. For example, an input could be This is a test string. So it is. or I must be OUT OF MY MIND. What was I thinking. (without the ). You may also assume that each word has a space after it and that there is exactly one space between words. All sentences end in a period. Do not count spaces as characters. import java.util.scanner; public class Exam2Program6 { public static int sentences(string str) { int a = 0; for (int i = 0; i < str.length(); i++){ char c = str.charat(i); if (c == '.') return a; public static int words(string str) { int a = 0; for (int i = 0; i < str.length(); i++){ char c = str.charat(i); if (c == ' ') return a; public static int characters(string str) { int a = 0; for (int i = 0; i < str.length(); i++){ char c = str.charat(i); if (c!= ' ') return a; Scanner keyboard = new Scanner(System.in); String instr = keyboard.nextline(); System.out.println("Characters: " + characters(instr)); System.out.println("Words: " + words(instr)); System.out.println("Sentences: " + sentences(instr));