Strings are sequences of characters that can be manipulated and combined in various ways. Common string operations include inserting variables, concatenating strings, determining string length, checking if a substring is contained, extracting substrings by location, and splitting strings into an array. The document provides examples of performing these operations in Java, Objective-C, and Swift.

1. Strings

2. What is a string?
• A sequence of characters.
• Strings can have different character encodings (UTF8,
ASCII)
• Strings in Objective-C, Swift and Java are immutable.
• In Objective-C, Swift and Java strings are interned.
• In C, strings are terminated by null. In Java, Objective-C
and Swift they are not which means their length is stored
internally.

3. Common operations
• Inserting variables in a string
• Concatenate (adding strings together / append)
• Length
• Contains a string
• Substring Location
• Substring Extraction
• Split

4. Exercises:
1. Create a string with your name
2. Create a string with ”Hello, “
3. Create an integer and a float with any value you like
4. Create a string that’s a comma-separated list of your
favorite foods.

5. Insert variables in a string
Java String y = String.format(”x = : %f", x);
String y = ”x = “ + x;
String y = ”x = “ + someObject.toString();
Objective-C NSString *str = [NSString stringWithFomat:@”%@”, object];
%d – integer
%f – float
%@ – calls description method on an object
Swift let str = “x = (variable)”
let str = String(format: “x = %f”, x)
1. Create a string containing “Float: 1.02 Integer:1”

6. Concatenating strings
Java String y = str1 + str2
String z = new StringBuilder(str1).append(str2).toString();
Objective-C NSString *str= [str1 stringByAppendingString:str2];
Swift let str = str1 + str2
1. Concatenate the “Hello “ string with the string of your name

7. Length
Java str.length();
Objective-C str.length
Swift str.characters.count
1. Print the length of the string containing your float and integer.

8. Contains substring
Java str.contains(str2)
Objective-C [str containsString:str2]
Swift str.containsString(str2) //objc method
1. Print “PizzaTime” if your string of favorite foods contains ”pizza”

9. Substring location
Java str.indexOf(str2) //first character
str.lastIndexOf(str2) //last character (right most occurance)
Objective-C NSRange range = [str1 rangeOfString:@”word"];
Swift str.rangeOfString(str2) //objc method
1. Get the location of a food in your list.

10. Get Substring
Java str.substring(3,5)
Objective-C [str1 substringWithRange:range]
Swift str1.substringWithRange(range) //objc method
1. Extract one food into a separate string.

11. Split
Java str.split(“,”);
Objective-C [str componentsSeparatedByString:@”,”]
Hint: NSRange r = NSMakeRange(location, length)
Swift str.componentsSeparatedByString(",")
1. Create an array of your favorite foods. Print the values each on a new line.