Common Mistakes You Are Doing in Your Java Programming Assignments

Java programming is one of the most widely accepted high-level programming languages due to java’s significant features. The features are,

  • Object-Oriented – Everything in Java is an object. The functionality these object offers are called functions. The programs that hold these functions are called classes.
  • Platform Independent – After compilation, java codes can be made to run on different platforms. This is very beneficial as you need to code once and never worry about the program’s platform.
  • Simple & Secure – Java is simple to understand and secure at the same time, employing public-key encryption.

It’s no wonder more, and more people thus choose java as the first programming language to learn. Schools and colleges offer courses carefully curated to include java as the programming language. This is forcing students to perform various tasks like assignments and papers, and presentations. It is also why more and more students pursuing their higher studies are looking online for help with java programming assignments. If you are amongst the many feeling terrified with your java assignments, then this blog is just for you.

Java programming is excellent if you are not finding bugs that you cannot handle. But if you are trying to find the bugs that are harder to debug, then rest assured, you will spend more time than you have expected. We will be providing you with a list of the most common errors that most of us face and the solutions to be used for your benefit.

In java, there are three types of error

  1. Java syntax error
  2. Java runtime error
  3. Java logical error

Allow us to elaborate,

Java Syntax Error –

This is the most common error most programmers face. As the name suggests, it often happens with not adhering to the proper syntax as java follows strict syntactical rules. Complier detects these errors while compiling. As for .java code to run across multiple platforms instead of for the whole code, ‘Bytecode’ is sent.

Using incorrect capitalization – Java uses’ Camel Case’ while defining any variables or classes. Most programmers make these kinds of mistakes while writing the code.

publicstaticvoidcreateNewZipFile(String locationZipFile)

// It is not same as,

publicstaticvoidcreateNewZipfile(String locationZipFile)


Missing Parenthesis – Methods in Java is defined as methodName(). While writing or calling any method, the inclusion of ‘()’ is mandatory. Without this, the compiler will throw compilation errors.

logger = LogFileConfigurator.getSystemLogFile;

// The method call is faulty

Missing curly brackets – Classes in Java along with loops are also include closed curly brackets. As the complexity based on functionality increases while defining any class, missing a curly bracket is a widespread way most programmers face syntax errors. IDE or Integrated Development Environment is the tool most of us use to write lines of code. IDE specifically uses highlighters for brackets. Using an IDE limits the chances of this type of errors.

publicAddFilesToZipFile() {


// Here closing curly bracket is missing.

Failure to import a class properly– This happens to most of the seasoned programmers a well. Failure to correctly import the library functions that hold the definition to any type needs to be considered Java works when the classes have definitions. This is especially true when we want to use any function as an API Application Programming Interface.;;



// Correctly imported library functions.

Forgetting to use Break or Return keywords –’Break’ keywords are used in ‘Cases’ that vary with output given the choice of input. Failure to include the ‘Break’ statement does exactly what a break in a car does. It stops progress further.

case ‘A’:

System.out.println(“Your favorite color is White!”);


      case ‘B’:

System.out.println(“Your favorite color is Black!”);


//Break will not work here, as the same is commented

Similarly, ‘Return’ is used when we expect our function to return a value. Not writing this statement, compiler searches for the same and not finding ‘Return’ throws exception.

public String getFileNumber() {

//return fileNumber;


//Commenting out the return throws an exception

Java cannot work without a Main method – The compiler will not capture this error, but the runtime engine will directly throw the error. All code in a project starts

from here.

public static void main (String args[])

// An example of the main method

Java Runtime Error –

This error only occurs when the code is compiled OK, but after creating the bytecode or .class file, the code doesn’t run properly. This needs to be fixed with a process called ‘debugging.’ Most of the time, students and developers face runtime errors as often when the code passes compilation and produces a result that is not desirable. Java virtual machine is responsible for detecting runtime errors. But with more and more programming errors, you will eventually understand that there are two possibilities that the error exists, failure to articulate the exact logic at the place and failure to anticipate a problem that already exists and can be handled.

Learn to proper use of Exceptions –There are multiple ways to create exceptions and be used to your benefit. There are various types of exceptions like,

  • Dividing an integer by zero exception.
  • Trying to access an element that is not in the Array’s range raises ArrayOutOfBound exception, as java Array starts with the position [0]
  • Trying to store non-compatible values in an Array, this often happens when there is a mismatch in the return type expected and the return type created by an operation,
  • Trying to store non-compatible values in an Array, this often happens when there is a mismatch in the return type exception and the return type created by an operation,

publicstaticint []calAverage(int[] a)

      //Expecting array but creating an integer


int average = 0;

for (inti =0;i<20;i++)


average += a[i];


return average / 20;



  • Trying to convert invalid string into a number.,

intnumber = Integer.parseInt(str);

Java Logical Error – 

Logical errors are those that occur because of the failure to write exact logic in the code. To find a logical fallacy, one needs to be vigilant and possess the qualities to challenge own work. As logical error doesn’t have any syntactical errors, the compiler doesn’t detect them. This is the most problematic error to find in the codes. The process involves anyone going through every line of code. A programming error that you discover when you’re debugging your code is very annoying. It can be hard to remove from your code without finding the exact cause of the problem, and you may never really know what happened unless you figure it out.

Null pointer exceptions –This can happen in an invalid variable declaration, leading to a null pointer being created. You should check whether the value assigned to the variable is greater than the number of objects. It would help if you fixed this by making sure that all things are in the correct schema. A critical aspect of good testing that cannot be neglected is the ability of the designer to test all possible configurations without missing any element. This is especially important in situations where the designs are dependent on other formats.

publicstaticvoid main (String[] args)


// Initializing a String variable with null value

String ptr = null;


// Checking if ptr.equals null or works fine.



/* This line of code throws NullPointerException

because ptr is null */

if (ptr.equals(“aba”))



System.out.print(“Not Same”);






} }

The null pointer exception can be handled using something called ‘NullPointerException,’ as shown in the above example.

Incorrect precedence of using operator– When two instructions in a program share the same precedence order, each instruction executes first. In java, you can specify an order of precedence different from the rest of the program, called priority order. There is only one precedence set in java, but with many operators that are precedence dependent. If the evaluation of a given operator is not essential, the system would not be overloaded.


publicstaticvoidmain(String args[]){


System.out.println(x++);//10 (11)


//The value of x is what it is storing right now.

System.out.println(x–);//12 (11)

//Not working on the precedence gives you logical errors.




Precision work based on floating point – As in any calculation, the real numbers provide some approximation to the precision. The floating-point numbers are not that precise. As in any measure, the real numbers give some approximation to the accuracy. The floating-point numbers have the problem of being too small for an entire computer and other machines and too big for the whole of a computer and other devices, depending on their power requirements.

floatc = 101.123456789123;

floatx = -125.563f;

floatq = 506.12789f;

//Float only stores 16 digits, so for higher digits please use double

double c = 101.123456789123456789;

Integer values for measurement – However, when you add numbers to an integer, that number isn’t the same everywhere. For that reason, you’re better off using factors in programming languages. Here’s how you can use factors in Java,

for(i = 1; i<= Number; i++) {

if(Number%i == 0) {

//i increase every time the loop iterates

System.out.format(” %d “, i);

Multiple things can go wrong while writing your java programming assignments, but you can quickly get rid of them following the solutions above. But if you still find yourself fixated on situations that are hard for you to figure out by yourself, please go online and look for help with java programming assignments. It might save you a lot of effort and stress.


By Alex Brown

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