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Problem description: Type Mismatch/Invalid Cast
Problem category: Compile-Time Problem

Diagnosis Difficulty: Easy
Difficulty to Fix: Easy


This problem usually occurs when you're trying to...

Problem description: byte/char/integer/long values wrapping around (either back to 0 or to a really negative number)
Problem category: Logic Error

Diagnosis Difficulty: Easy-Hard
Difficulty to...

Problem description: Array Indices/Off by 1 errors
Problem category: Logic Problem/ Runtime Error

Diagnosis Difficulty: Easy-medium
Difficulty to Fix: Easy-medium


Array indices in Java...

Problem description: == operator or equals() method
Problem category: Logic Problems

Diagnosis Difficulty: Easy-Medium
Difficulty to Fix: Easy-Medium


A common problem among many beginning...

Problem description: Forgetting to initialize a variable
Problem category: Runtime problem

Diagnosis Difficulty: Easy-medium
Difficulty to Fix: Easy-medium


This problem occurs when you...

Problem description: Case Sensitivity, spelling
Problem category: Compile-time Problems

Diagnosis Difficulty: Easy
Difficulty to Fix: Easy


Java is case sensitive, as well as spelling...

Problem description: Referencing Non-static variables/methods in a static way
Problem category: Compile-time Problems

Diagnosis Difficulty: Easy
Difficulty to Fix: Easy-medium


This problem...

Problem description: Code outside of a method
Problem category: Compile-time Problems

Diagnosis Difficulty: Medium
Difficulty to Fix: Easy-medium


The two most common incarnations of this...

Problem description: Abstract method in non-abstract class
Problem category: Compile-time Problems

Diagnosis Difficulty: Easy-medium
Difficulty to Fix: Easy


This problem usually occurs when...

Problem description: Parenthesis, Brackets, Braces, etc. mis-match
Problem category: Compile-time Problems

Diagnosis Difficulty: Easy
Difficulty to Fix: Easy


This problem occurs when you...

Here's a template you can use if you want to contribute. Try to stick to the template as much as you can, but some deviation is ok. Try to make your post as generic as possible without losing too...

Introduction

Here's a list of common problems you can encounter when programming in Java. Anyone else can feel free to add to this list. I'll try to update this "table of contents" when I can. Do...