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More Compile-Time Errors

Explore common compile-time errors in Java programming, including missing parentheses, braces, double quotes, concatenation and arithmetic operators, and uninitialized variables. Understand how compilers detect these errors and learn tips for identifying and fixing them effectively to improve your debugging skills.

We'll cover the following...

Missing parenthesis

Suppose we accidentally omit the closing parenthesis from a println statement. For example, consider the program below. Notice the result of its compilation after you click the RUN button.

Java
public class Debug8
{
   public static void main(String[] args)
   {
      System.out.println("Welcome!";
   } // End main
} // End Debug8

The compiler is precisely correct in identifying the mistake!

What if we had omitted the opening parenthesis instead, so that the program appears as shown below. Click the RUN button.

Java
public class Debug9
{
   public static void main(String[] args)
   {
      System.out.println"Welcome!");
   } // End main
} // End Debug9

Although the error messages do not mention a missing parenthesis, hopefully they will help you to see the mistake.

Missing brace

Braces, like parentheses, must occur in open-close matching pairs. The program shown below has two open braces but only one close brace. Click the RUN button to see how the compiler handles this situation.

Java
public class Debug10
{
   public static void main(String[] args)
   {
      int anInteger = 10;
      System.out.println("The integer is " + anInteger);
   } // End main

The word parse means to analyze syntactically. The error message indicates that the compiler has reached the last available statement in the program and now can tell that the program is incomplete. Something needs to follow the last brace. It is up to us to figure out that ...