public static void main(String[] args) {
    Double temperature = 0.0;
    Double result = 0.0;
    
    String menuChoise = "1. Celsius to Fahrenheit \n2. Fahrenheit to Celsius";
    int anyChoiseMenu = 3;
    System.out.println("Chose a conversion");
    System.out.println(menuChoise);
    Scanner sc = new Scanner(System.in);
    while (true) {
        try {
            anyChoiseMenu = sc.nextInt();
            if (anyChoiseMenu == 1) {
                System.out.println("What temperature you wanna convert: ");
                temperature = sc.nextDouble();
                result = (1.8) * temperature + 32;
                System.out.println("Result: " + result + " Fahrenheit");
                break;
            } else if (anyChoiseMenu == 2) {
                System.out.println("What temperature you wanna convert: ");
                temperature = sc.nextDouble();
                result = ((5 * (temperature - 32.0)) / 9.0);
                System.out.println("Result: " + result + " Celsius");
                break;
            } else {
                System.out.println("Wrong number. Try again!");
                sc.nextLine();
            }
        } catch (Exception e) {
            System.out.println("Only numbers bro.");
            System.out.println(menuChoise);
            sc.nextLine();
            continue;
        }
    }
}

import java.util.InputMismatchException;
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String menuChoice = "\nChoose a conversion: \n1. Celsius to Fahrenheit \n2. Fahrenheit to Celsius";
int menu;
while (true) {
System.out.println(menuChoice);
try {
menu = sc.nextInt();
} catch (InputMismatchException e){
System.out.println("Invalid input, only numbers are allowed!");
sc.nextLine();
continue;
}
if (menu >= 3) {
System.out.println("Wrong number. Try again!");
} else {
System.out.print("What temperature you wanna convert: ");
double temperature = sc.nextDouble();
if (menu == 1) {
temperature = 1.8 * temperature + 32;
} else if (menu == 2) {
temperature = (temperature - 32) / 1.8;
}
String grade = (menu == 1)? "Celsius": "Fahrenheit";
System.out.format("Result: %.2f " + grade + '\n', temperature);
break;
}
}
}
}

public static void main(String... args) {
Scanner scan = new Scanner(System.in);
scan.useLocale(Locale.ENGLISH);
while (true) {
System.out.println("Chose a conversion:");
System.out.println("1. Celsius to Fahrenheit");
System.out.println("2. Fahrenheit to Celsius");
System.out.println("3. Exit");
System.out.print("> ");
int menu = scan.nextInt();
if (menu == 1) {
System.out.print("What temperature you wanna convert: ");
double celsius = scan.nextDouble();
double fahrenheit = 1.8 * celsius + 32;
System.out.format(Locale.ENGLISH, "Result: %.2f Fahrenheit\n", fahrenheit);
} else if (menu == 2) {
System.out.println("What temperature you wanna convert: ");
double fahrenheit = scan.nextDouble();
double celsius = (fahrenheit - 32) / 1.8;
System.out.format(Locale.ENGLISH, "Result: %.2f Celsius\n", celsius);
} else if (menu == 3)
break;
else
System.out.println("Wrong number. Try again!");
System.out.println();
}
}