S. Cakici S. Cakici - 15 days ago 9
Java Question

How does my program run when I don't have a main method

I am studying java course in my college and we are using a library called acm. But when we write a code we don't create a main method. "public void run(){}" acts as a main method. Explain please.

For an example here's a program that I created.

import acm.program.ConsoleProgram;
import acm.util.RandomGenerator;

public class Assignment3 extends ConsoleProgram {

private static final long serialVersionUID = 1L;
private RandomGenerator rgen = RandomGenerator.getInstance();

public void run() {
final int QUESTION_AMOUNT = 5;

println("Welcome to the Math Quiz! You have " + QUESTION_AMOUNT + " questions to answer! Good luck!");

for (int i = 0; i < QUESTION_AMOUNT; i++) {
askQuestion();
}

println("End of the quiz!");
}

public void askQuestion() {
int num1, num2, kidanswer, realanswer;
String operation = "";
boolean x = rgen.nextBoolean();

if (x == true) {
operation = "+";
} else {
operation = "-";
}

if (operation == "-") {
num1 = rgen.nextInt(0, 20);
num2 = rgen.nextInt(0, num1);
} else {
num1 = rgen.nextInt(0, 20);
num2 = rgen.nextInt(0, 20 - num1);
}

String question = ("What is " + num1 + " " + operation + " " + num2 + " = ");

if (operation == "-") {
realanswer = num1 - num2;
} else {
realanswer = num1 + num2;
}

kidanswer = readInt(question);

int i = 0;
while (i < 2) {
if (kidanswer == realanswer) {
println("That is correct! Well done!");
break;
} else {
kidanswer = readInt("Wrong answer. Please try another answer: ");
i++;
if (i == 2) {
if (kidanswer == realanswer) {
println("That is correct! Well done!");
} else {
println("Sorry :( Out of tries! The answer was: " + realanswer);

}
}
}
}
}
}

Answer

Because: