COP3330 Homework 4- Interfaces Solution

Any class that implements the Java’s CharSequence interface must override the following abstract methods: charAt, length and subSequence. For example, the class String implements CharSequence. That is why you see the three methods (charAt, length and subSequence) appear (as overriden methods) in the list of public methods of the class String.

In this HW, you will be asked to implement the built-in Java interface CharSequence. You will be provided with two classes: The DriverClass class and the Code class that implements CharSequence (from the util package). The class Code has int [][] codeArray, int numRows, int numColumns as its private fields, and it is already equipped with the code that loads and print the array codeArray. Your task is to override the methods charAt, length and subSequence as indicated below:

Assume that the array codeArray is:

125 53 63 63
78 59 71 45
69 90 95 93

Then override the :
1- char charAt (int index) to return the character whose ascii/Unicode code is at index. Given the array above, if index is 6, the element of the array code to consider is 71, and the character to return is G (the ascci code for the G is 71).

Want to check? System.out.println((char) 71);

2- int length() to return how many characters are loaded in the array (which is the number of integers in the array). In the case of the array provided here, length returns 12

3- String subSequence(int start, int end) returns the string formed by concatenating all the characters corresponding to the integers from index start to index end. For example subsequence(1,5) returns 5??N;

A scatelon code is provided at the end of this HW. Once again, your task is to provide the code for the three methods: charAt, length and subSequence. (Do not change the Driver class!)






Sample Run 1:

Enter row 1: 125 53 63 63
Enter row 2: 78 59 71 45
Enter row 3: 69 90 95 93
Testing charAt: Enter your index [a number greater or equal to 0 and less or equal to 11]: 6
Enter how many rows and how many columns to load: 3 4 Assume that the user will enter numbers between 1 and 20

The character located at index 6 is: G

Testing length: there are 12 characters.

Testing subSequence: Enter start and end indexes: 1 5
The subsequuence is: 5??N;


Goodbye!







Assume that the user will enter a numbers between 0 and (number of rows times number of columns – 1)
Assume that the user will enter two nonnegative integers sunch that the first one is less or equal to the second one, and that both of the entered numbers are between 0 and (number of rows times number of columns – 1)


Sample Run 2:

Enter how many rows and how many columns to load: 2 8
Enter row 1: 195 63 63 63 69 92 85 95
Enter row 2: 78 59 71 45 85 67 70 33

Testing charAt: Enter your index [a number greater or equal to 0 and less or equal to 11]: 0 The character located at index 0 is: Ã

Testing length: there are 16 characters.

Testing subSequence: Enter start and end indexes: 12 15
The subsequuence is: UCF!


Goodbye!


import java.util.Scanner;

public class DriverClass {
public static void main(String args[]) { int numRows, numColumns; int index, start, end; char charAtIndex; int length;
String subSequence;

Scanner myScan = new Scanner(System.in);

System.out.print("Enter how many rows and how many columns to load: "); numRows = myScan.nextInt();
numColumns = myScan.nextInt();

Code codeObject = new Code(numRows, numColumns);

codeObject.loadCodeArray(numRows, numColumns); codeObject.printCodeArray(numRows, numColumns);
// __________________________________________
System.out.print(" Testing charAt: Enter your index [a number greater or equal to 0 and less or equal to ");
System.out.print((numRows * numColumns - 1) + "]:");
index = myScan.nextInt();

charAtIndex = codeObject.charAt(index);

System.out.println("The character located at index " + index + " is: " + charAtIndex);

// __________________________________________
length = numRows * numColumns;

System.out.println(" Testing length: there are " + length + " characters.");

// __________________________________________
System.out.print(" Testing subSequence: Enter start and end indexes:
");
start = myScan.nextInt(); end = myScan.nextInt();

subSequence = codeObject.subSequence(start, end); System.out.println("The subsequuence is: " + subSequence);
// __________________________________________
System.out.println(" Goodbye!");

}
}




//_____________________________________ class Code implements CharSequence {

private int[][] codeArray;
private int numRows, numColumns;

public Code(int numRows, int numColumns) {
this.numRows = numRows;
this.numColumns = numColumns;
codeArray = new int[numRows][numColumns];
}

public void loadCodeArray(int numRows, int numColumns) { Scanner myScan = new Scanner(System.in);
int i, j;
for (i = 0; i < numRows; i++) {
System.out.print("Enter Row " + (i + 1) + ": "); for (j = 0; j < numColumns; j++) {
codeArray[i][j] = myScan.nextInt();
}
}

}

public void printCodeArray(int numRows, int numColumns) {

int i, j;
System.out.println(" _____________ ");
for (i = 0; i < numRows; i++) {

for (j = 0; j < numColumns; j++) { System.out.print(codeArray[i][j] + " ");
}
System.out.println("");
}

}

// ______________THE CODE ABOVE IS TO REMAIN UNCHANGED______________________
@Override
public char charAt(int index) { // Add your code here...
}

@Override
public int length() {
// Add your code here...
}

@Override
public String subSequence(int start, int end) { // Add your code here...
}

}