My if and else coding doesn't work

Question

First of all, I am new to this website and coding so please forgive my rookie mistakes, second of all my problem is, I intended to make a quiz via eclipse software using java coding (obviously). But everytime i run it, even when i type in the right answer it reacts like i typed in the wrong answer. Could you please point out my mistake?

import java.util.*;

public class Quiz {

public static void main(String[] args) {
    // TODO Auto-generated method stub


    @SuppressWarnings("resource")
    Scanner in = new Scanner(System.in);
    System.out.println("Hi! Welcome to the Quiz! Please insert your username.");
    String userName = in.nextLine();
    System.out.println("Welcome " + userName + "! Let's start! Your first question is what is the capital of Norway?");
    String answer = in.nextLine();
    if (answer == ("Oslo"))
    System.out.println("Good Job! Your next question is how many states are there in U.S.A.?");

else        
{
    System.out.println("You've failed!");
}
    {

        @SuppressWarnings("unused")
    String answer1 = in.nextLine();
    if (answer1 == ("50"))
    System.out.println("Well done! Your next question is where did the first football world cup happen?");
    else        
    {
        System.out.println("You've failed!");
    }
    String answer2 = in.nextLine();
    if (answer2 == ("Uruguay"))
    System.out.println("Well done! Your next question is");
    else        
    {
        System.out.println("You've failed!");
    }
    }
    }
    }

Answer 1

It has to do with comparing strings.

Your situation should be solved when you change your if condition to:

 if (answer.equals("Oslo")) { // Do something } 

When using equals() you compare the contents of what you try to compare. If you use == it actually compares the references of what you try to compare. Thus where the object is stored (answer) to the given string "Oslo", which is not equal and therefore returns false.

In addition to your question in the comments

To get a quick solution you can use nested if-else statements.

You can also use a new if statement for each question, just below each other. This would require a bit more rewriting of your code. See the example:

public class App {

   public static void main(String[] args) {

        Scanner in = new Scanner(System.in);
        System.out.println("Hi! Welcome to the Quiz! Please insert your username.");
        String userName = in.nextLine();
        System.out.println("Welcome " + userName + "! Let's start! Your first question is what is the capital of Norway?");
        String answer = in.nextLine();
        if (!answer.equals("Oslo")) {
            System.out.println("You've failed!");
        }

        System.out.println("Good Job! Your next question is how many states are there in U.S.A.?");
        answer = in.nextLine();
        if (!answer.equals("50")) {
            System.out.println("You've failed!");
        }
        System.out.println("Well done! Your next question is where did the first football world cup happen?");
    }
}

However, as you can see code becomes pretty repetitive, so making use of function would be a good next step. See the next example:

public class AppWithFunction {

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);
        System.out.println("Hi! Welcome to the Quiz! Please insert your username.");
        String userName = in.nextLine();
        System.out.println("Welcome " + userName + "! Let's start!");

        handleQuestion(in, "Your first question is what is the capital of Norway?", "Oslo");
        handleQuestion(in, "Your next question is how many states are there in U.S.A.?", "50");
}

private static void handleQuestion(Scanner in, String questions, String answer) {
    System.out.println(questions);
         if (!in.nextLine().equals(answer)) {
            System.out.println("You've failed!");
        }
    }
}

It might be a bit out of your scope for the moment, but if you would have a bunch of questions, storing these in a map (question = key, answer = value), iterate over them and handle them accordingly would be a good next step.(Maybe a nice self-assigned new exercise later on;)).