EASYTUTORGUIDEJava • Java 26

Generic Bounds and Wildcards

Chapter 25 of 60 • beginner to advanced • code example for every topic

5 topics5 code examples10 Q&A

25.1 Generic Types 25.2 Generic Methods 25.3 Bounds/Constraints 25.4 Generic Collections 25.5 Generic Design

25.1 Generic Types

This topic teaches Generic Types as part of Generic Bounds and Wildcards. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

public class Main { public static void main(String[] args) { // Generic Types
System.out.println("Java example"); } }

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Generic Types. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

25.2 Generic Methods

This topic teaches Generic Methods as part of Generic Bounds and Wildcards. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

public class Main { static int add(int a,int b){return a+b;} public static void main(String[] args){System.out.println(add(3,4));} }

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Generic Methods. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

25.3 Bounds/Constraints

This topic teaches Bounds/Constraints as part of Generic Bounds and Wildcards. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

public class Main { public static void main(String[] args) { // Bounds/Constraints
System.out.println("Java example"); } }

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Bounds/Constraints. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

25.4 Generic Collections

This topic teaches Generic Collections as part of Generic Bounds and Wildcards. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

import java.util.*;
public class Main { public static void main(String[] args){ List<Integer> xs=new ArrayList<>(List.of(3,1,2)); Collections.sort(xs); System.out.println(xs); } }

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Generic Collections. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

25.5 Generic Design

This topic teaches Generic Design as part of Generic Bounds and Wildcards. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

public class Main { public static void main(String[] args) { // Generic Design
System.out.println("Java example"); } }

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Generic Design. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.