My input is not taken by if else if statment [duplicate]

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I'm generating a random number from 1 to 100 and showing it to user and then I will get 20 chances to to guess that random number. The response should be either YES or NO but right now when I run this program it just takes input from user and end the execution it is not visiting the if else if loop

Code

public static void main(String args[])
{
    Random rand = new Random();
    int rand_int1 = rand.nextInt(100);
    System.out.println("Random value is = " + rand_int1);

    int n = 20;

    Scanner userinput = new Scanner(System.in);

    System.out.println("is your number is form 0 to 50 ?");
    String ans1 = userinput.nextLine();
    System.out.println("ans : " + ans1);

    if (ans1 == "yes") {
        System.out.println("number is more then 50");
    }
    else if (ans1 == "no") {
        System.out.println("number is less then 50");
    }
}

Example Output

Random value : 23

is your number is more then or equal to 50?
ans : No

Later, I will add more code so this will also be in the output:

is your number is less then or equal to 25?
ans : Yes