Create a system with three classes (one of which is a test driver): 1. Create a

Question

Create a system with three classes (one of which is a test driver):

1. Create a CodeBot class (CodeBot.java) that has two private fields: className and code (both are of type String). Create a no-arg constructor that hard-codes the class name (e.g., Hello) and initializes the code field with a string that represents a simple Java class that displays something (e.g, “hello, world”) to standard output (e.g.,"public class Hello { public static void main(String[] args) { System.out.println("hello, world");}}"). Create another constructor that requires that the class name and code are provided by the caller (i.e., a constructor with two String parameters). Both constructors should call the private “saveCode” method (see below) to save the code to the file system as part of constructing a CodeBot object. Create a private helper method named saveCode that is based on Listing 12.14 on page 477 (Liang, 10th edition). This method should have a void return type and result in a file being written in your project’s root directory. Create a public compile method that accepts no input arguments. If the class name is not found in the code, the method will throw a CompilationExceptionwith the message “Class name must be found in code.” Otherwise, it will print out a message: “The program className.java has compiled successfully.”

2. Create a CompilationException class ( CompilationException.java) that is a subclass of Exception (i.e., a custom checked exception).

3. Create a CodeBotTest class (CodeBotTest.java) that instantiates a CodeBot object using the no-arg constructor and then call the compile method. It should then create another CodeBot object using the other constructor with className = “Hello2” and code = "public class { public static void main(String[] args) {System.out.println("hello, world");}}" and then call the compile method.

Here is a sample run:

Program Hello.java has compiled successfully.

Exception in thread "main" CompilationException: Class name must be found in code.

at CodeBot.compile(CodeBot.java:33)

at CodeBotTest.main(CodeBotTest.java:7)

The second time you run your program, it should print out the following message:

File Hello.java already exists.

Explanation / Answer

Given below is the code for the question.
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CodeBot.java
======

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

public class CodeBot {
private String className, code;

public CodeBot(){
className = "Hello";
code = "public class Hello { public static void main(String[] args) { System.out.println("hello, world");}}";
saveCode();
}

public CodeBot(String className, String code){
this.className = className;
this.code =code;
saveCode();
}

private void saveCode(){
try {

File f = new File(className + ".java");

if(f.exists())

{

System.out.println("File " + f.getName() + " already exists");

System.exit(0);

}

PrintWriter pw = new PrintWriter(f);

pw.println(code);
pw.close();
} catch (FileNotFoundException e) {
System.out.println(e.getMessage());
}
}

public void compile() throws CompilationException{
if(code.indexOf(className) == -1)
throw new CompilationException("Class name must be found in code.");

System.out.println("The program " + className + ".java has compiled successfully");
}

}

CompilationException.java
------
public class CompilationException extends Exception {

public CompilationException() {
}

public CompilationException(String message) {
super(message);
}

}

CodeBotTest.java
--------
public class CodeBotTest {
public static void main(String[] args) throws CompilationException {
CodeBot b1 = new CodeBot();
b1.compile();

CodeBot b2 = new CodeBot("Hello2", "public class { public static void main(String[] args) {System.out.println("hello, world");}}");
b2.compile();
}
}

output
=======
The program Hello.java has compiled successfully
Exception in thread "main" CompilationException: Class name must be found in code.
at CodeBot.compile(CodeBot.java:32)
at CodeBotTest.main(CodeBotTest.java:8)

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