Java compareTo一步一步执行(Java compareTo step by step execution)

 我基本了解Java compareTo方法按lexicographically compares两个字符串。 我在这里阅读了基础知识Java中的字符串比较 
 
 我有以下示例： 
 
public class CompareTo {
   public static void main(String args[]) {
       String str1 = "String";
       String str2 = "compareTo";
       String str3 = "String";
       int var1 = str1.compareTo( str2 );
       System.out.println("str1 & str2 comparison: "+var1);

       int var2 = str1.compareTo( str3 );
       System.out.println("str1 & str3 comparison: "+var2);
   }
}
 
 我得到var1 = -16和var2 = 0 。 
 
 如果有人一步一步地向我解释这个Lexicographic comparison ，那将会有很大的帮助。 
 
 谢谢。 

I have basic understanding that Java compareTo method lexicographically compares two strings. I have read basics here String Comparison in Java
 
I have following example:
 
public class CompareTo {
   public static void main(String args[]) {
       String str1 = "String";
       String str2 = "compareTo";
       String str3 = "String";
       int var1 = str1.compareTo( str2 );
       System.out.println("str1 & str2 comparison: "+var1);

       int var2 = str1.compareTo( str3 );
       System.out.println("str1 & str3 comparison: "+var2);
   }
}
 
I get var1 = -16 and var2 = 0.
 
If someone explains me this Lexicographic comparison step by step It would be of great help.
 
Thanks.