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Summary - Variables

Combine int, double and String to write a profile card.

Summary - Variables

In this group you learned Java's basic variable types:

  • int: for integers
  • double: for decimals
  • boolean: for true/false
  • String: for text
  • final: for constants

Variable names use camelCase, constants use ALL_CAPS. Now combine them and write a profile card.

Practice Write a profile card

Write a Main class with a main method. Assign "Alex" to String name and 28 to int age. Print both with println.

Sample solution

Main.java
public class Main {
    public static void main(String[] args) {
        String name = "Alex";
        int age = 28;
        System.out.println(name);
        System.out.println(age);
    }
}

Expected output

Alex
28

Next steps

You now know the basic variable types. In the next groups you will see:

  • Type casting and the Math class
  • String methods (length, substring)
  • Conditionals (if, switch)
  • Loops (for, while)
  • Arrays and collections

To keep the knowledge fresh, write your own small programs. Declare variables, assign values, and print with println. With practice the concepts will settle in.

Practice Final constant with a profile

Write a Main class with a main method. Assign "London" to final String CITY. Print it with println.

Sample solution

Main.java
public class Main {
    public static void main(String[] args) {
        final String CITY = "London";
        System.out.println(CITY);
    }
}

Expected output

London

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Match the types

Term Meaning
int Integer
double Decimal
boolean Logical
String Text

2 Define a constant

Question 
final int MAX_USERS = ____;
Answer 
final int MAX_USERS = 100;

Explanation: A final constant takes an integer without quotes.

All lessons in Beginner

1 Java basics

  1. What is Java?
  2. The main method
  3. Comments
  4. Class skeleton
  5. javac and java
  6. Summary - Java basics

2 Variables

  1. int and double
  2. boolean
  3. String
  4. Naming variables
  5. final variables
  6. Summary - Variables

3 Data types

  1. Primitive types
  2. Type casting
  3. String concatenation
  4. Math class
  5. BigInteger and BigDecimal
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add/subtract
  3. Multiply/divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic
  2. Comparison
  3. Logical
  4. Bitwise
  5. Assignment and increment
  6. Summary - Operators

6 String basics

  1. length and charAt
  2. equals and equalsIgnoreCase
  3. indexOf and substring
  4. toUpperCase and trim
  5. String.format
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. else and else if
  3. Nested if
  4. switch
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. do-while
  4. break and continue
  5. for-each
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Updating quantity
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Filling arrays
  4. Multi-dimensional arrays
  5. Copying arrays
  6. Summary - Arrays

11 Array methods

  1. Arrays.sort
  2. Arrays.toString
  3. Arrays.binarySearch
  4. Arrays.copyOf
  5. Arrays.fill
  6. Summary - Array methods

12 Collections

  1. ArrayList
  2. add and get
  3. HashMap
  4. put and get
  5. HashSet
  6. Summary - Collections

13 Methods

  1. Defining methods
  2. return
  3. void methods
  4. Method overloading
  5. Scope
  6. Summary - Methods

14 Method parameters

  1. Primitive parameters
  2. Object parameters
  3. varargs
  4. Multiple values via array
  5. final parameters
  6. Summary - Method parameters

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 String builder

  1. StringBuilder
  2. append
  3. insert and delete
  4. reverse
  5. toString
  6. Summary - String builder

17 Input and output

  1. Scanner
  2. nextInt and nextLine
  3. System.out.printf
  4. BufferedReader
  5. try-with-resources
  6. Summary - Input and output

18 Enum

  1. Declaring enums
  2. values and valueOf
  3. Enum fields
  4. Enum methods
  5. switch with enum
  6. Summary - Enum

19 Exception basics

  1. try/catch
  2. finally
  3. throw
  4. Exception hierarchy
  5. Multiple catch
  6. Summary - Exception basics

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together