6: Strings, Arrays and Collections

6 Strings, Arrays and Collections

6.1 Print 2D Array

The following code creates a 3 x 3 tic-tac-toe grid filled with Xs.

 1: void tictactoe()
 2:    {
 3:       String [][] grid = new String[3][3];
 4: 
 5:       for(int i = 0; i<grid.length; i++)
 6:       {
 7: 	  for (int j = 0; j<grid.length; j++)
 8: 	  {
 9: 	      grid[i][j] = "X";
10: 	  }
11:       }
12:       printArray(grid);
13: 
14:    }

Write a method that will print a 2D array of any size. Test it using the 3 x 3 tic-tac-toe grid given above

6.1.1 Example

1: tictactoe()
2:  *** Output ***
3:  | X | X | X |
4:  | X | X | X |
5:  | X | X | X |

6.2 Chess Board

Create an 8 x 8 Array to represent a chess board. Print out the array with alternate ‘X’ and ‘O’ entries as shown in the example:

6.2.1 Example

 1: chess();
 2:  *** Output ***
 3:  | X | O | X | O | X | O | X | O |
 4:  | O | X | O | X | O | X | O | X |
 5:  | X | O | X | O | X | O | X | O |
 6:  | O | X | O | X | O | X | O | X |
 7:  | X | O | X | O | X | O | X | O |
 8:  | O | X | O | X | O | X | O | X |
 9:  | X | O | X | O | X | O | X | O |
10:  | O | X | O | X | O | X | O | X |

6.3 Digits to Words

Write a method that will convert digits into words

6.3.1 Example

1: System.out.println(digitsToWords("35001922"));
2:  *** Output ***
3: Three Five Oh Oh One Nine Two Two

6.4 Time to Words

Write a method that will convert time to words. For example, 4:10 is “Ten past four” and 4:55 is “Five to Five”

6.4.1 Example

 1: System.out.println(timeToWords("2:05"));
 2: System.out.println(timeToWords("2:47"));
 3: System.out.println(timeToWords("12:00"));
 4: System.out.println(timeToWords("2:00"));
 5: System.out.println(timeToWords("12:30"));
 6: System.out.println(timeToWords("4:29"));
 7: System.out.println(timeToWords("7:25"));
 8: System.out.println(timeToWords("12:45"));
 9: System.out.println(timeToWords("12:55"));
10:  *** Output ***
11: five past two
12: thirteen minutes to two
13: twelve o'clock
14: two o'clock
15: half past past twelve
16: twenty nine minutes past four
17: twenty five past seven
18: Quarter to one
19: five to one

6.5 Morse Code Arrays

Write a program using arrays that translates plain text into morse code.

A B C D E F G
.- -… -.-. -.. . ..-. –.
H I J K L M
…. .. .— -.- .-..
N O P Q R S T
-. .–. –.- .-.
U V W X Y Z
..- …- .– -..- -.– __..

6.5.1 Example

1: String s = "I never saw a purple cow"
2: 
3: morse(s)
4:  *** Output ***
5: .. / -. . ...- . .-. / ... .- .-- / .- / .--. ..- .-. .--. .-.. . / -.-. --- .--

6.6 Demorse Code Arrays

Now write a program using arrays that translates morse back to plain text.

6.6.1 Example

1: String s = ".. -././...-/./.-. .../.-/.-- .- .--./..-/.-./.--./.-../. -.-./---/.--"
2: 
3: deMorse(s)
4:  *** Output ***
5: "I never saw a purple cow"

6.7 Morse Code Hashmap

Rewrite the Morse Code program using Hashmap

6.7.1 Example

1: String s = "I never saw a purple cow"
2: morseHash(s)
3:  *** Output ***
4: .. / -. . ...- . .-. / ... .- .-- / .- / .--. ..- .-. .--. .-.. . / -.-. --- .--

6.8 Demorse Code Hashmap

Rewrite the Demorse Code program using Hashmap

6.8.1 Example

1: String s = ".. -././...-/./.-. .../.-/.-- .- .--./..-/.-./.--./.-../. -.-./---/.--"
2: deMorseHash(s)
3:  *** Output ***
4: "I never saw a purple cow"

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