Do Loop变量无法解析为变量

Question

I have this code in which I loop until the user enters a -1. However, I get the error :

key cannot be resolved to a variable

I have used this code before and I didn't have a problem with it, so I'm not sure why I'm having this problem.

System.out.println("\nEnter a number, -1 to stop : ");
do {
  int key = scan.nextInt();
  int result = interpolationSearch(integerArray, key);
  if (result != -1) {
    System.out.println("\n"+ key +" element found at position "+ result);
  }
    break;
} while (key != -1);    // quit 
System.out.println("stop");
}

Answer 1

You need to declare key outside the do loop and can get the nextInt every time the loop runs through. Also there is no need of break statement in the loop.

System.out.println("\nEnter a number, -1 to stop : ");
int key;
do {
  key = scan.nextInt();
  int result = interpolationSearch(integerArray, key);
  if (result != -1) {
    System.out.println("\n"+ key +" element found at position "+ result);
  }      
} while (key != -1);    // quit 
System.out.println("stop");
}

Answer 2

You need to declare int key outside of your do loop. Because it is declared inside the loop, the while condition doesn't know about it. This is called being out of scope. Here are some examples and an explaination of scope http://java.about.com/od/s/g/Scope.htm .

Change it to this:

System.out.println("\nEnter a number, -1 to stop : ");
int key;
do {
  key = scan.nextInt();
  int result = interpolationSearch(integerArray, key);
  if (result != -1) {
    System.out.println("\n"+ key +" element found at position "+ result);
  }
    break;
} while (key != -1);    // quit 
System.out.println("stop");
}