Common Programming Errors by Beginners in Java

Jan 27, 20162 likes689 views

This document discusses 10 common errors that beginners encounter when programming in Java. 1) The "javac is not recognized" error occurs when the Java environment variables are not set correctly. 2) When compiling, the file name must have a ".java" extension. 3) When executing, only the class name should be passed without the ".java" extension, and the class must contain a main method. 4) The "file not found" error occurs when the file is not in the current working directory or the file name is incorrect.

$C o n c e p t s o f J a v a P r o g r a m m i n g Page 9 Common Errors for Beginners Consider a class named Test is saved in a file Test.java and saved in D: Java directory class Test { public static void main(String rk[]) { System.out.println("Error???"); } } Case 1: javac is not recognized as an internal or external command This error occurs because you have not set the environment variable in your machine. Follow the following steps: 1. Copy the path up to bin folder in jdk. (C:Program FilesJavajdk1.8.0_65bin) 2. Right click on My Computer icon on desktop. Then follow the following Properties  Advanced system settings  Advanced  Environment Variables 3. In System Variables click on New and fill the Variable name and Variable Value as shown below:$

C o n c e p t s o f J a v a P r o g r a m m i n g Page 10
Case 2: Annotation processing
While compiling your Java program file name must be given with .java extension.
 javac Test.java
Case 3: Could not find or load main class Test.java
While executing your Java program name of the class is to be passed (without any extension)
which contains the main method:
public static void main (String rk[])
NOTE: In a normal java program, if you will try to execute a class which does not contain the
above mentioned main method, then you will get the same error message. As the java run time
environment expects that method in the class whose name you are passing during the execution.

C o n c e p t s o f J a v a P r o g r a m m i n g Page 11
Case 4: file not found: Test.java
This error occurs because the file named Test.java is not located in the current working
directory. So check whether the file is saved in that location or not?
Then either change the current working directory in your command prompt or change the name
of the file.
In the above case the file is saved in D: Java but we are working in directory C:Usershp
So we need to change the directory as shown below:
The same error may be seen if you are in the correct working directory but the file name is
different while compiling that.
If we write any other file name instead of Test.java (e.g. javac Test1.java or javac test.java), It
will result in the same error.

C o n c e p t s o f J a v a P r o g r a m m i n g Page 12
Case 5: Reached end of file while parsing
This error occurs when you have missed any closing braces in your program as in this program:
class Test
{
public static void main(String rk[])
{
System.out.println("Error???");
}

C o n c e p t s o f J a v a P r o g r a m m i n g Page 13
Case 6: class, interface, or enum expected
This error arises due to different reasons.
(A) When you have added some extra braces as shown in the code below:
(B) When you have used class/interface keywords incorrectly as in the code below class is
written as Class. Java is case sensitive and all the keywords are in lower case.
class Test
{
public static void main(String rk[])
{
System.out.println("Error???");
}
} }
Class Test
{
public static void main(String rk[])
{
System.out.println("Error???");
}
}

C o n c e p t s o f J a v a P r o g r a m m i n g Page 14
Case 7: class TestJava is public, should be declared in a file named TestJava.java
This error occurs when you have created a public class but saved in a file with some other name.
Every public class must be saved in a .java file named as the name of the class, whereas other
classes can be saved with any name.
NOTE: It means that in a .java file you can define N number of classes and interfaces but
at most one of them can be public and the name of the file must be same as the name of the
public class.
 The above classes can be saved in a single .java file but the file must
be named as TestJava.java.
class Test {
public static void main(String rk[])
{
System.out.println("Error???");
}
}
public class TestJava {
void testingJava()
{
System.out.println("Inside testingJava Method...");
}
}

C o n c e p t s o f J a v a P r o g r a m m i n g Page 15
Case 8: cannot find symbol
This error occurs when you are referring to a variable which does not exist and the ^ is pointing
to that variable.
In the above case string symbol does not exist as we have used string instead of String (String is
a predefined class in java.lang package).
Case 9: package does not exist
Similar to the previous case we have used system instead of System in our program. System is a
predefined class in java.lang package.

C o n c e p t s o f J a v a P r o g r a m m i n g Page 16
Case 10: ‘;’ expected
This error occurs because we have missed ‘;’ after the statement.

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1. C o n c e p t s o f J a v a P r o g r a m m i n g Page 9 Common Errors for Beginners Consider a class named Test is saved in a file Test.java and saved in D: Java directory class Test { public static void main(String rk[]) { System.out.println("Error???"); } } Case 1: javac is not recognized as an internal or external command This error occurs because you have not set the environment variable in your machine. Follow the following steps: 1. Copy the path up to bin folder in jdk. (C:Program FilesJavajdk1.8.0_65bin) 2. Right click on My Computer icon on desktop. Then follow the following Properties  Advanced system settings  Advanced  Environment Variables 3. In System Variables click on New and fill the Variable name and Variable Value as shown below:

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3. C o n c e p t s o f J a v a P r o g r a m m i n g Page 11 Case 4: file not found: Test.java This error occurs because the file named Test.java is not located in the current working directory. So check whether the file is saved in that location or not? Then either change the current working directory in your command prompt or change the name of the file. In the above case the file is saved in D: Java but we are working in directory C:Usershp So we need to change the directory as shown below: The same error may be seen if you are in the correct working directory but the file name is different while compiling that. If we write any other file name instead of Test.java (e.g. javac Test1.java or javac test.java), It will result in the same error.

4. C o n c e p t s o f J a v a P r o g r a m m i n g Page 12 Case 5: Reached end of file while parsing This error occurs when you have missed any closing braces in your program as in this program: class Test { public static void main(String rk[]) { System.out.println("Error???"); }

5. C o n c e p t s o f J a v a P r o g r a m m i n g Page 13 Case 6: class, interface, or enum expected This error arises due to different reasons. (A) When you have added some extra braces as shown in the code below: (B) When you have used class/interface keywords incorrectly as in the code below class is written as Class. Java is case sensitive and all the keywords are in lower case. class Test { public static void main(String rk[]) { System.out.println("Error???"); } } } Class Test { public static void main(String rk[]) { System.out.println("Error???"); } }

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7. C o n c e p t s o f J a v a P r o g r a m m i n g Page 15 Case 8: cannot find symbol This error occurs when you are referring to a variable which does not exist and the ^ is pointing to that variable. In the above case string symbol does not exist as we have used string instead of String (String is a predefined class in java.lang package). Case 9: package does not exist Similar to the previous case we have used system instead of System in our program. System is a predefined class in java.lang package.

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