Test 1 Solutions

Test 1s, and their solutions. I am not showing the output of the programs. Just paste them into eclipse and run them to see what it does.

This is the test for one of the sections:

1. (25%) What does the following program print out when run?
   
   

   	public static void main(String[] args) {
   		boolean bool = true;
   		int i = 0;
   		for (i=0; i < 5; i++){
   			System.out.println(i);
   			if (bool && (i % 2 == 0) )
   				System.out.println("Ob");
   			else if (i < 3)
   				System.out.println("La");
   			else if (i % 2 == 0 || i > 3 )
   				System.out.println("Di");
   		}
   		System.out.println(i < 10);
   	}
             

2. (25%) What does the following program print out when run?
   

   	public static void main(String[] args) {
   		String word = "CCBA";
   		while (word.length() > 0){
   			char c = word.charAt(0);
   			System.out.print(c); //notice: print
   			word = word.substring(1);
   			int x = 0;
   			switch (c) { //watch out for missing breaks!
   				case 'A':
   					x = 4;
   				case 'B':
   					x = 2;
   					break;
   				case 'C':
   					x = 3;
   			};
   			for (int i=0; i < x; i++){
   				System.out.print("*"); //print (NOT println)
   			}
   			System.out.println(""); //move to next line
   		}
   	}
           

3. (25%) Write a program that asks the user to enter a
   word and then prints YES if the first 3 characters of the word
   are the same as the last 3 characters (and in the same order).
   Otherwise, or if the word has fewer than 3 characters, the
   program prints NO. Some sample runs:
   

   Enter word:alphabet
   NO
   ---we run the program again---
   Enter word:abalataba
   YES
   ---we run the program again---
   Enter word:javaisjav
   YES
   ---we run the program again---
   Enter word:javaisajv
   NO
   ---we run the program again---
   Enter word:jav
   YES
   ---we run the program again---
   Enter word:b
   NO
             

   Answer:
   

   	public static void main(String[] args) {
   		Scanner keyboard = new Scanner(System.in);
   		System.out.print("Enter word:");
   		String word = keyboard.next();
   		if (word.length() < 3)
   			System.out.println("NO");
   		else if (word.substring(0,3).equals(word.substring(word.length() - 3))) {
   			System.out.println("YES");
   		}
   		else
   			System.out.println("NO");
   	}
   

4. (25%) Write a program that ask the user to enter a
   sentence and then prints out that same sentence but with every
   other character turned into its uppercase equivalent. For
   example:
   

   Enter message:this program is impossible to write
   tHiS PrOgRaM Is iMpOsSiBlE To wRiTe
   ---we run the program again---
   Enter message:fun in the sun
   fUn iN ThE SuN
             

   Answer:
   

   	public static void main(String[] args) {
   		Scanner keyboard = new Scanner(System.in);
   		System.out.print("Enter message:");
   		String msg = keyboard.nextLine();
   		String result = "";
   		for (int i=0; i < msg.length(); i++){
   			String letter = msg.substring(i,i+1);
   			if (i%2 == 0) {
   				result += letter;
   			}
   			else {
   				result += letter.toUpperCase();
   			}
   		}
   		System.out.println(result);
          }
   

This is the test for the other section.

1. (25%) What does the following program print out when run?
   
   

   	public static void main(String[] args) {
   		int i = 5;
   		int sum = 0;
   		for (i=5; i > 0; i--){
   			System.out.println(i);
   			sum += (i * 2);
   			if (i > 2 && i < 4)
   				System.out.println("Ob");
   			else if (i % 3 > 0)
   				System.out.println("La");
   		}
   		System.out.println(sum);
   	}
             

   
   
2. (25%) What does the following program print out when run?
   

   	public static void main(String[] args) {
   		String word = "ABCCAB";
   		while (word.length() > 0){
   			char c = word.charAt(0);
   			System.out.print(c); //notice: print
   			word = word.substring(2);
   			int x = 0;
   			switch (c) { //watch out for missing breaks!
   				case 'A':
   					x = 3;
   				case 'B':
   					x = 1;
   					break;
   				case 'C':
   					x = 4;
   			};
   			if (x <= 1)
   				System.out.println(" alan");
   			else if (x <= 3)
   				System.out.println(" turing");
   			else
   				System.out.println(" lives");
   		}
   	}
           

3. (25%)
   Write a program that asks the user to enter a word. If the
   word has an 'a' in it then the program will print out the letter
   that comes after the first 'a' in the word (from
   left-to-right). If there are no 'a's or if the 'a' is the last
   character in the word then the program will print out
   "OOPS". Below are some sample runs.

   Enter word:eventful
   OOPS
   ---we run the program again---
   Enter word:java
   v
   ---we run the program again---
   Enter word:nova
   OOPS
   ---we run the program again---
   Enter word:animation
   n
   

   Answer:
   

   	public static void main(String[] args) {
   		Scanner keyboard = new Scanner(System.in);
   		System.out.print("Enter word:");
   		String word = keyboard.next();
   		int aIndex = word.indexOf('a');
   		if (aIndex == -1) {
   			System.out.println("OOPS");
   		} 
   		else if (aIndex == word.length() -1 ){
   			System.out.println("OOPS");
   		}
   		else {
   			System.out.println(word.charAt(aIndex + 1));
   		}
   	}
   

4. (25%) Write a program that asks the user to enter a
   sentence. The program will then print out the total number of
   times the letter 'a' appears in the sentence, as well as the total number of
   times the two letters 'an' appear (in that order). Below are
   some sample runs.

   Enter message:banana
   Number of As = 3
   Number of ANs = 2
   ---we run the program again---
   Enter message:the music of the night
   Number of As = 0
   Number of ANs = 0
   ---we run the program again---
   Enter message:are you suggesting that coconuts migrate?
   Number of As = 3
   Number of ANs = 0
   

   Answer:
   

   	public static void main(String[] args) {
   		Scanner keyboard = new Scanner(System.in);
   		System.out.print("Enter message:");
   		String msg = keyboard.nextLine();
   		int numAs =0;
   		int numANs = 0;
   		for (int index = 0; index < msg.length(); index++){
   			if (msg.charAt(index) == 'a') {
   				numAs++;
   				//take advantage of short-circuit evaluation
   				if (index + 1 < msg.length() && msg.charAt(index + 1) == 'n') 
   					numANs++;
   			}
   		}
   		System.out.println("Number of As = " + numAs);
   		System.out.println("Number of ANs = " + numANs);
   	}