Why doesn't if process the results from the scanner?

Question

Java

Scanner inData = new Scanner(System.in);
System.out.println("Would you like to continue?");
String answer = inData.nextLine();
if (answer == "yes"){
System.out.println("Test!");
}

I can't understand at all. If you just display it on the screen, it displays yes without problems. If you hardcode answer and then compare, it works correctly. However, if you take inData.next() or inData.nextLine(), the comparison does not work for some reason. Test is only output if != yes. What's the catch?