I´d wanted to compile a simple Java "Hello World" program like it was repesented on the GeeksforGeeks Hello World Tutorial, by using gcj in Linux Ubuntu. This is the source code: But gcj threw two errors: (.text+0x18): undefined reference to main collect2: error: ld returned 1 exit status Original output from the terminal: I´d take attention on the requirement, that

GCJ throws error: “Undefined reference to main” when compiling

I´d wanted to compile a simple Java “Hello World” program like it was repesented on the GeeksforGeeks Hello World Tutorial, by using gcj in Linux Ubuntu. This is the source code:

class HelloWorld 
{ 
    public static void main(String args[]) 
    { 
        System.out.println("Hello, World"); 
    } 
}

But gcj threw two errors:

(.text+0x18): undefined reference to main
collect2: error: ld returned 1 exit status

Original output from the terminal:

gcj -o helloworld HelloWorld.java
/usr/lib/gcc/i686-linux-gnu/4.6/../../../i386-linux-gnu/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: error: ld returned 1 exit status

I´d take attention on the requirement, that the .java file should be named after the class which holds main:

Important Points :

The name of the class defined by the program is HelloWorld, which is same as name of file(HelloWorld.java). This is not a coincidence. In Java, all codes must reside inside a class and there is at most one public class which contain main() method.

By convention, the name of the main class(class which contain main method) should match the name of the file that holds the program.

What am I doing wrong?

Answer

You are missing the --main= option, from the documentation, this option is used when linking to specify the name of the class whose main method should be invoked when the resulting executable is run.

gcj -o helloworld --main=HelloWorld HelloWorld.java

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Answer