我在运行教科书附带的示例代码时遇到问题。我JDK7在OS XMountain Lion 上使用。StringMutation.java编译正常，但运行 javaStringMutation.class给我以下错误
Could not find or load main class StringMutation.class.
我在 StringMutation.java 和 StringMutation.class 所在的同一目录中运行 javac StringMutation.java 和 java StringMutation.class。
如果重要的话，我将 Java SE7 设置为 Java Preferences 中的最高优先级。感谢您的帮助。
这是示例代码：
public class StringMutation
{
public static void main (String[] args)
{
String phrase = "Change is inevitable";
String mutation1, mutation2, mutation3, mutation4;
System.out.println ("Original string: \"" + phrase + "\"");
System.out.println ("Length of string: " + phrase.length());
mutation1 = phrase.concat (", except from vending machines.");
mutation2 = mutation1.toUpperCase();
mutation3 = mutation2.replace ('E', 'X');
mutation4 = mutation3.substring (3, 30);
// Print each mutated string
System.out.println ("Mutation #1: " + mutation1);
System.out.println ("Mutation #2: " + mutation2);
System.out.println ("Mutation #3: " + mutation3);
System.out.println ("Mutation #4: " + mutation4);
System.out.println ("Mutated length: " + mutation4.length());
}
}