Java String Basics & Concatenation

What is a String?

• A String is an object in Java that stores text.
• Strings are made up of characters (letters, numbers, symbols).
• In Java, String starts with a capital S because it is a class.

Creating a String

String name = "Joe";
String school = "Klein Collins";

Printing Strings

System.out.println(name);
System.out.println("Hello world");

• println prints and moves to a new line.
• print prints without moving to a new line.

String Concatenation

• Concatenation means joining Strings together.
• Java uses the + operator to concatenate Strings.

Basic Example

String firstName = "Joe";
String lastName = "Cusack";

String fullName = firstName + " " + lastName;
System.out.println(fullName);

Output

Joe Cusack

Concatenating Strings and Numbers

String greeting = "Hello " + "World";

Hello World

int age = 16;
System.out.println("Age: " + age);

Age: 16

Order Matters (Left to Right)

System.out.println(10 + 5 + " apples");
System.out.println("Apples: " + 10 + 5);

Output

15 apples
Apples: 105

Common String Methods

.length()

Returns the number of characters in a String.

String word = "Java";
System.out.println(word.length());

4

.equals()

Used to compare String values.

String a = "hello";
String b = "hello";

System.out.println(a.equals(b));

true

Escape Characters

Escape characters let you place special characters inside Strings.

System.out.println("He said \"Hello\"");
System.out.println("Line1\nLine2");

• \" → quotation mark
• \n → new line

Common Mistakes to Avoid

❌ Forgetting Quotes

String name = Joe;   // ERROR

✅ Correct Version

String name = "Joe";

❌ Comparing Strings with ==

✅ Use .equals() instead.

Key Takeaways