title: error: incompatible types: java.lang.String cannot be converted to String
body: <p>I'm taking a Java class for college, and was working on some given tasks. This is the code I wrote for it.</p>
  
  <pre><code>public class String
  {
   public static void main(String[] args)
   {
    String city = "San Francisco";
    int stringLength = city.length();
    char oneChar = city.charAt(0);
    String upperCity = city.toUpperCase();
    String lowerCity = city.toLowerCase();
  
    System.out.println(city);
    System.out.println(stringLength);
    System.out.println(oneChar);
    System.out.println(upperCity);
    System.out.println();
    }
   }
  </code></pre>
  
  <p>which yielded these results</p>
  
  <pre><code>C:\Users\sam\Documents\Java&gt;javac String.java
  String.java:8: error: incompatible types: java.lang.String cannot be 
  converted to String
            String city = "San Franciso";
                          ^
  String.java:9: error: cannot find symbol
              int stringLength = city.length();
                                     ^
  symbol:   method length()
  location: variable city of type String
  String.java:10: error: cannot find symbol
              char oneChar = city.charAt(0);
                                 ^
  symbol:   method charAt(int)
  location: variable city of type String
  String.java:11: error: cannot find symbol
              String upperCity = city.toUpperCase();
                                     ^
  symbol:   method toUpperCase()
  location: variable city of type String
  String.java:12: error: cannot find symbol
              String lowerCity = city.toLowerCase();
                                     ^
  symbol:   method toLowerCase()
  location: variable city of type String
  5 errors
  </code></pre>
  
  <p>I've tried searching for an answer but I didn't really find anything that helps. Any help is appreciated, thanks.</p>