Why Scanner.next of "C" is not equal to String "C" [duplicate]

This question already has an answer here:

• How do I compare strings in Java? 23 answers

My code is:

import java.util.Scanner;

public class EvaluateTemperature {

public static void main(String[] args)
{
    Scanner temperatureScanner = new Scanner(System.in);
    Scanner unitScanner = new Scanner(System.in);
    Double  converted = 0.0;

    System.out.println("What's the temperature now?");
    int temperature = temperatureScanner.nextInt();

    System.out.println("Is it Celsius or Fahrenheit?");
    String unit = unitScanner.next();

    System.out.println(unit == "C");

    if (unit == "C")
    {
        converted = temperature * 1.8 + 32;
    }

    if (unit == "F")
    {
        converted = (temperature - 32) / 1.8;
    }

    System.out.println(converted);

    temperatureScanner.close();
    unitScanner.close();
    }
}

The input and output in the console is:

What's the temperature now?
40
Is it Celsius or Fahrenheit?
C
false
0.0

It seems that the block code of if has not been executed because the value unit is not equal to “C” or “F”.

With the code System.out.println(unit == "C”); of which the output is “false”, it can be proved that even thought I input “C” to the value unit, the value unit is not equal to “C”.

WHY?

Thanks.