highschool/Grade 10/Computer Science/ICS4U1/Array Manipulation Notes.md

Arrays

What is an Array?

• Object used to store a list of values

• All values in array are the same type -Eg. int, double, char, string, etc

• Used to store a large number of data

• Easy to access any element in the array

How to Declare

• Declaring an array to up to 10 words

String array[] = new String[10];

• Declaring an array and initializing variables at the same time:

String array[] = {"s", "d", "f"};

String Manipulataion

• length() to find the length of a string

• stringName.charAt(0) will output the first character

• Each character in a string has a positio. String positions start at 0

• stringName.indexOf("T") will output the index number that the letter T belongs to

• stringName.substring(3) will output all characters after the index #

• Eg. string stringName = "Jim hates math"

  • Output: hates math

• First # is for the index that you want and last number is for the index that you don’t want

• stringName2 = " i hate math "

• stringName2.trim();

  • Output: i hate math

• stringName.toLowerCase() makes every character a lower case letter

• stringName.toUpperCase() makes every character an upper case letter

• concat()

• stringname1.concat(stringname2); will put both string into 1 word

• stringname.replace("a", "p"); will replace every a with p

• stringname1.equals(stringname2); will return true of false depending on whether the two contain the same value

• stringname1.compareTo(stringname2); is for alphabetical order

  • if the condition above is \(`< 0`\), name1 is before name2. \(`> 0`\), name1 is after name2, if \(`=0`\), its the same string

Sorting

static void ImprovedBubbleSorted(int arr[]) {
    boolean isSorted = false;
    int j = 1;
    while(!isSorted) {
        isSorted = true;
        for(int i = 0; i < arr.length - j; i++) {
            if(arr[i]> arr[i + 1]) {
                int t = arr[i];
                arr[i] = arr[i + 1];
                arr[i + 1] = t;

                isSorted = true;
            }
        }
        j++;
    }
}

Searching

boolean found=false;
System.out.println("Enter the word you want to search");
String word = sc.next();
for(int i=0; i<arr.length; i++) {
    if(arr[i].equals(word)) {
        found=true;
    }
}
if(found) {
    System.out.println("The word was found");
}
else {
    System.out.println("The word was not found");
}

Searching Continued

boolean found=false;
System.out.println("Enter the word you want to search");
String word = sc.next();
int pos=0;
for(int i=0; i<arr.length; i++) {
    if(arr[i].equals(word)) {
        found=true;
        pos=i;
    }
}
if(found) {
    System.out.println("The word was found at index: " + pos);
}
else {
    System.out.println("The word was not found");
}

Conclusion

• Arrays are very useful when problem solving when a large numbe of data is involved
• Organize large sets of data
• Variety of ways you can access information in an array