StringTokenizer错误

Question

这是我第一次在分数计算器中使用tokenizer。我尝试了尽可能多地遵循语法，但得到了这个丑陋的错误：

Fraction.java:78: error: no suitable constructor found for 
StringTokenizer(Fraction,String,boolean)
    StringTokenizer parser = new StringTokenizer(oldMeasure, "/", true);                             
constructor StringTokenizer.StringTokenizer(String) is not applicable
  (actual and formal argument lists differ in length)
constructor StringTokenizer.StringTokenizer(String,String) is not applicable
  (actual and formal argument lists differ in length)
constructor StringTokenizer.StringTokenizer(String,String,boolean) is not applicable
  (actual argument Fraction cannot be converted to String by method invocation conversion)

下面是代码

    public void read(Scanner theKeyboard)
    {
    StringTokenizer parser = new StringTokenizer(oldMeasure, "/");
    if(parser.countTokens() !=2)
        throw new RuntimeException("bad format for fraction");
    myNumerator = Integer.parseInt(parser.nextToken());
    myDenominator = Integer.parseInt(parser.nextToken());
    }

Answer 1

传入构造函数的第一个参数必须是String。它是一个Fraction，不是一个String。找到把它转换成String的方法，Java编译器不能帮你做到这一点，而且在不太了解Fraction类型的情况下可以得到的建议很少。