Flash cards
Review the key moves
What is the main idea behind Java Strings?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Put the learning moves in the order that makes the concept easiest to apply.
Strings are used for storing text.
A String variable contains a collection of characters surrounded by double quotes ( "" ):
StringString Length
A String in Java is actually an object, which means it contains methods that can perform certain operations on strings.
For example, you can find the length of a string with the length() method:
Example
String txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
System.out.println("The length of the txt string is: " + txt.length());More String Methods
There are many string methods available in Java.
For example
- The toUpperCase() method converts a string to upper case letters.
- The toLowerCase() method converts a string to lower case letters.
Example
String txt = "Hello World";
System.out.println(txt.toUpperCase()); // Outputs "HELLO WORLD"
System.out.println(txt.toLowerCase()); // Outputs "hello world"Finding a Character in a String
The indexOf() method returns the index (the position) of the first occurrence of a specified text in a string (including whitespace):
Example
String txt = "Please locate where 'locate' occurs!";
System.out.println(txt.indexOf("locate")); // Outputs 7Java counts positions from zero. 0 is the first position in a string, 1 is the second, 2 is the third ...
You can use the charAt() method to access a character at a specific position in a string:
Example
String txt = "Hello";
System.out.println(txt.charAt(0)); // H
System.out.println(txt.charAt(4)); // oComparing Strings
To compare two strings, you can use the equals() method:
Example
String txt1 = "Hello";
String txt2 = "Hello";
String txt3 = "Greetings";
String txt4 = "Great things";
System.out.println(txt1.equals(txt2)); // true
System.out.println(txt3.equals(txt4)); // falseRemoving Whitespace
The trim() method removes whitespace from the beginning and the end of a string:
Example
String txt = " Hello World ";
System.out.println("Before: [" + txt + "]");
System.out.println("After: [" + txt.trim() + "]");