Java Tutorial

Java Project: Contact Book

Store contacts in a TreeMap from name to number, then add, find, and list them in order.

What you will build

A TreeMap keeps names sorted. put adds, get finds, forEach lists.

TreeMap of names

Example

import java.util.Map;
import java.util.TreeMap;

public class Main {
  public static void main(String[] args) {
    Map book = new TreeMap<>();
    book.put("Ada", "555-0100");
    book.put("Kai", "555-0142");
    book.put("Rin", "555-0199");
    System.out.println("Kai -> " + book.get("Kai"));
    book.forEach((name, n) -> System.out.println(name + " " + n));
  }
}

Practice

Compile the complete program at /java/try.
Change one input value and compile again.
Replace a hardcoded number with Scanner when you want typed input.

FAQ: Java Project: Contact Book

Common questions about this page.

What is the StudyGrid Java tutorial?

The StudyGrid Java tutorial is a full beginner-to-advanced track: syntax, types, input, loops, methods, classes, collections, generics, maps, and lambdas. Each chapter has copy-and-run examples.

Should I run java contacts project examples locally for better learning?

Yes. Use the browser editor on StudyGrid for a quick check, then Download the example and run it on your computer. Local runs show real errors and the real toolchain, which is one of the fastest ways to learn java contacts project in this Java Java lesson (Java Project: Contact Book).

Is the Java editor the same as Try Python or Try C++?

No. Try Java compiles with javac at /java/try and shows stdout plus compiler messages. Try Python stays at /try. Try C++ stays at /cpp/try. Java lessons never open those editors.

Do I need to install a JDK to learn Java?

No. Open a chapter, click Try it in Java, and compile in the browser. You can also download a .java file and compile locally with javac.

Where should I start the Java tutorial?

Start at Java Intro, then Get Started and Syntax. After the first program, continue to output, variables, and if-else. After classes, open Java Examples, then generics, map, and lambdas. Use Next at the bottom of each chapter.

Is the Java tutorial free?

Yes. The Java workshop on StudyGrid (studygrid.in) is free: dashboard, chapters, and the compile-and-run editor.