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Summary - String basics

Combine length, substring and format to write a business card.

Summary - String basics

In this group you learned String methods:

  • length/charAt: length and character access
  • equals/equalsIgnoreCase: content comparison
  • indexOf/substring: search and slice
  • toUpperCase/trim: transformation
  • String.format: formatting

These methods are the basic tools to process, search, transform and format string data. Now combine them and write a business card.

Practice Write a business card

Write a Main class with a main method. Assign "Alex" to String name and "Engineer" to String title. Assign name + " - " + title to String card. Print card and card.length() with println.

Sample solution

Main.java
public class Main {
    public static void main(String[] args) {
        String name = "Alex";
        String title = "Engineer";
        String card = name + " - " + title;
        System.out.println(card);
        System.out.println(card.length());
    }
}

Expected output

Alex - Engineer
15

Tips

A few tips from this group:

  • Always use equals for String comparison; == is not reliable.
  • Trim user input that may have extra spaces first.
  • Check indexOf result against -1.
  • Strings are immutable; assign transformations to a new variable.
  • Use String.format to format output.

Combined with conditionals and loops, these basics let you write powerful programs.

Practice Business card with String.format

Write a Main class with a main method. Assign "Alex" to String name and 28 to int age. Assign String.format("%s - %d", name, age) to String card. Print card with println.

Sample solution

Main.java
public class Main {
    public static void main(String[] args) {
        String name = "Alex";
        int age = 28;
        String card = String.format("%s - %d", name, age);
        System.out.println(card);
    }
}

Expected output

Alex - 28

Questions and answers

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

1 Match the methods

Term Meaning
length() Length
equals() Compare
substring() Slice
format() Format

2 Complete the substring call

Question 
String first = name.____(0, 1);
Answer 
String first = name.substring(0, 1);

Explanation: substring(0, 1) gives the first character.

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