1. Tonga Institute of Higher Education
String Manipulation
Tonga Institute of Higher Education

2. Introduction
We know how to combine strings together and why this is useful
Why is it useful to break strings apart?
Extraction of data
Example: My birthday is “ ”. How can we determine the year from this string?
How do we break strings apart?

3. String.charAt Method - 1
A char datatype is different from a String datatype
A char is only 1 character (letter)
‘a’
‘5’
A String contains many characters
“Hello”
“Sione”
You can get the char for each location in a string using the charAt method

4. String.charAt Method - 2 A String is like an array of characters1 2 3 4
Index
A String is like an array of characters
Each cell of this array contains 1 character
To get a character located at an index, we can use the charAt method
Prints H

5. String.subString Method - 1l o 1 2 3 4
Index
Use the subString method to get a smaller string from a larger string
Example: To get “Sione” from “Sione Tupou”

6. String.subString Method - 2l o 1 2 3 4
Index 1 2
The first method has only 1 parameter
It returns everything from that index to the end of the string
Prints “lo”

7. String.subString Method - 3l o 1 2 3 4
Index 1 2
The second method has only 2 parameter
It returns everything from the first index up to the second index
Prints “ll”

8. String.indexOf Method - 1l o 1 2 3 4
Index
Use the indexOf method to get the index number of a char or a string
Example: To find that the index of the first ‘l’ char is 2
-1 is returned if the char or string doesn’t exist 1 2 3 4

9. String.indexOf Method - 2l o 1 2 3 4
Index 1 2 3 4
Returns 1
Find index of
characters
Returns -1

10. String.indexOf Method - 3l o 1 2 3 4
Index 1 2 3 4
Returns 2
Find index of
Strings
Returns 3
Start searching from this index

11. String.length Method
To get the number of characters in a string, use the length method
Returns 5

12. More Methods Available
trim – Removes whitespace before and after string
toUpperCase – Changes all characters to upper case
toLowerCase - Changes all characters to lower case
Check the API documentation for a complete list of the methods available