When using the Scanner function in Java, how do I set the input equal to a String in my "if" statement? [duplicate]

This question already has an answer here:

• How do I compare strings in Java? 23 answers

I'm trying to make a program that asks two questions and based off the answers to the questions, I have a generated response. It's like 20 questions but with only two questions (from ProgrammingByDoing.com). However, I can't seem to get my if statements to work as the program always bypasses them. I think I am incorrectly setting the input String equal to another String.

Here's my code:

import java.util.Scanner;

public class TwentyQuestions

{

public static void main( String[] args )
{
    Scanner keyboard = new Scanner(System.in);

    System.out.println("TWO QUESTIONS!");
    System.out.println("Think of an object, and I'll try to guess it.");
    System.out.println(" ");

    String first_answer;
    String second_answer; 

    System.out.println("Question 1) Is it animal, vegetable, or mineral?");
    first_answer = keyboard.next();

    if ( first_answer == "animal")
    {
        System.out.println("Question 2) Is it bigger than a breadbox?");
        second_answer = keyboard.next();
        if ( second_answer == "no")
        {
            System.out.println("My guess is that you are thinking of a squirrel");
        }
        else
        {
            System.out.println("My guess is that you are thinking of a moose");
        }

    }

    else if ( first_answer == "vegetable")
    {
        System.out.println("Question 2) Is it bigger than a breadbox?");
        second_answer = keyboard.next();
        if ( second_answer == "no")
        {
            System.out.println("My guess is that you are thinking of a carrot");
        }
        else
        {
            System.out.println("My guess is that you are thinking of a watermelon");
        }
    }
    else if ( first_answer == "mineral")
    {
        System.out.println("Question 2) Is it bigger than a breadbox?");
        second_answer = keyboard.next();
        if ( second_answer == "no")
        {
            System.out.println("My guess is that you are thinking of a paper clip");
        }
        else
        {
            System.out.println("My guess is that you are thinking of a Camaro");
        }
    }
    System.out.println("I would ask if I'm right, but I don't actually care.");

}

}