App termination loop

Question

Type the end-of-file indicator to terminate
*On UNIX/Linux/Mac OS X type d then press Enter
*On Windows type z then press Enter
new to java and i cant figure out how to code this, i tried using a while but i keep having clashing types in thepublic double minimum3 Scanner inputs,
been trying this today
double num1;
double num2;
double num3;
String z = "z";
          Scanner input = new Scanner(System.in);
               System.out.println("to terminae pogramon UNIX/Linux/Mac OS X type d then press enter");
               System.out.println("on windows type z then hit enter to exit");
if (input.next() = "z")
System.exit(0);
else
               System.out.println("enter first number");
               num1 = input.nextDouble();
               System.out.println("enter second number");
               num2 = input.nextDouble();
               System.out.println("enter third number");
               num3 = input.nextDouble();
my program goes fine until trying ti implement tat bit of a loop any ideas?

Answer 1

First and perhaps most importantly you almost never want to compare objects using == (String is an Object).
When you use == with objects you are comparing Object references. This will only return true if the two references are both pointing to the same object.
Instead you should use the equals method to compare Objects (like Strings) for equality.
Second I am not entirely sure what you want but if you want to have a while loop that executes on multiple possible conditions you could do something like this instead...
public void myMethod(){
   String aString = // read from user
   while(!validTerminator(aString)){
     // stuff
public boolean validTerminator(String aString){
  if(aString.equals("z")){
    return true;
  return aString.equals("d");
}