CS 101 Computer Programming Statements Review++

Reviewed so far.. Variables Constants Order of Execution Boolean expressions and variables if statements, if-else statements nested if statements loops: while statements, for statements Nested loops CS 101 | Özyeğin University2 int x = 10; private static final int SIZE = 50; boolean withinLimits = true; if(x 100) { withinLimits = false; } while(x < 100) {... while(y < 100) {... }

Exercise CS 101 | Özyeğin University import acm.program.*; public class ExecutionOrder extends ConsoleProgram { public void run() { int x = 10; /* 1 */ while(x < LIMIT) {/* 2 */ if(x%2 != 0) {/* 3 */ x += 3;/* 4 */ } else { x *= 10;/* 5 */ } private static final int LIMIT = 100; /* 6 */ } What is the order of execution? What is the value of x at the end?

Nested Loops CS 101 | Özyeğin University i:0,j:3 – i:0,j:2 – i:0,j:1 – i:1,j:3 – i:1,j:2 – i:1,j:1 – i:2,j:3 – i:2,j:2 – i:2,j:1 – import acm.program.*; public class Stars extends ConsoleProgram { public void run() { for(int i = 0; i < N; i++){ for(int j = N; j > 0; j--){ print("i:" + i + ",j:" + j + " - "); } private static final int N = 3; }

Exercise CS 101 | Özyeğin University Write a ConsoleProgram that outputs N rows of stars in the format shown below import acm.program.*; public class Stars extends ConsoleProgram { public void run() { /* TODO */ }

Exercise CS 101 | Özyeğin University Write a ConsoleProgram that outputs N rows of stars in the format shown below import acm.program.*; public class Stars extends ConsoleProgram { public void run() { for (int i = 0; i < 10; i++) { for (int j = 0; j <= i; j++) { print("*"); } println(""); }

Exercise CS 101 | Özyeğin University Now modify the program to print out rows of stars in the format shown below import acm.program.*; public class Stars extends ConsoleProgram { public void run() { /* TODO */ }

Exercise CS 101 | Özyeğin University Now modify the program to print out rows of stars in the format shown below import acm.program.*; public class Stars extends ConsoleProgram { public void run() { for (int i = 0; i < 10; i++) { for (int j = 0; j < 10-i ; j++) { print("*"); } println(""); }

Exercise Write a Java program that reads N positive integers and prints the maximum of those.

public class MaxOfNIntegers extends ConsoleProgram { public void run() { println("This program reads " + N + " *positive* integers,"); println("and prints the maximum."); int maximum = 0; for(int i=0; i < N; i++) { int value = readInt("Enter > "); if(value <= 0) { println("Please enter a POSITIVE integer!"); i--; // Decrement i so that we read the number again. } else if(value > maximum) { maximum = value; } println("Maximum is " + maximum); } private static final int N = 5; }

Exercise Write a Java program that reads integers from the users as long as they are positive, and finally prints the maximum of the numbers.

public class MaxOfIntegerList extends ConsoleProgram { public void run() { println("This program reads positive integers,"); println("and prints the maximum."); println("The program exits when the user enters a non-positive value."); int maximum = 0; while(true) { int value = readInt("Enter > "); if(value <= 0) break; if(value > maximum) { maximum = value; } if(maximum == 0) { println("You did not enter any positive integers."); } else { println("Maximum is " + maximum); } private static final int N = 5; }

Exercise Write a Java program that reads N positive integers and prints the maximum two of those.

public void run() { println("This program reads " + N + " *positive* integers,"); println("and prints the *two* maximum."); int maximum = 0; int secondMaximum = 0; for(int i=0; i < N; i++) { int value = readInt("Enter > "); if(value <= 0) { println("Please enter a POSITIVE integer!"); i--; // Decrement i so that we read the number again. } else if(value > maximum) { secondMaximum = maximum; maximum = value; } else if(value > secondMaximum) { secondMaximum = value; } println("Maximum is " + maximum); println("Second maximum is " + secondMaximum); }

Exercise Write a Java program that helps me decide how to travel. – If I'll travel for less than 1 km, I'll walk in any condition. – If I'll travel for less than 5 km, biking is my priority. – If I'll travel for more than 500 km, I'll fly in any condition. – I can ride my bike if the temperature is between 8 and 28 degrees. – I'll drive my car otherwise. Try to use as few boolean conditions as possible, and with exactly 4 println()’s.

public class TravelAssistant extends ConsoleProgram { public void run() { println("This programs helps the programmer"); println("decide on the means of transportation."); int distance = readInt("How many km will you travel? "); int temperature = readInt("What's the temperature? "); if(distance < 1) { println("Walk."); } else if(distance > 500) { println("Fly."); } else if(distance = 8 && temperature <= 28) { println("Bike."); } else { println("Drive."); } }

Exercise Implement the Checkerboard example using a single loop (instead of the nested loop). public class CheckerboardSingleLoop extends GraphicsProgram { public void run() { double sqSize = (double) getHeight() / N_ROWS; for (int n = 0; n < N_ROWS * N_COLUMNS; n++) { double i = n / N_COLUMNS; double j = n % N_COLUMNS; GRect sq = new GRect(j * sqSize, i * sqSize, sqSize, sqSize); add(sq); sq.setFilled((i+j) % 2 == 0); } private static final int N_ROWS = 10; private static final int N_COLUMNS = 8; }

Exercise Implement a graphical Java program in which a ball continuously scrolls from left to right.

public class ScrollingBall extends GraphicsProgram{ // Named constants can be defined at the top or the bottom of the class. private static final int BALL_SIZE = 50; private static final int PAUSE_TIME = 50; public void run() { GOval ball = new GOval((getWidth()-BALL_SIZE)/2, (getHeight()-BALL_SIZE)/2, BALL_SIZE, BALL_SIZE); ball.setFilled(true); ball.setFillColor(Color.RED); add(ball); int dx = 10; while(true) { // forever running! ball.move(dx, 0); if(ball.getX() > getWidth()) ball.setLocation(0, ball.getY()); pause(PAUSE_TIME); } public void init() { setSize(500,300); }