带循环的缺少返回语句错误-JAVA

Question

我在最后一个括号中丢失了一个return语句错误，我也不知道为什么。 该方法基本上采用一个字符串，该字符串与学生的课程及其所处的当前调查问题相对应。 外部if语句与主题相对应（例如：数学，科学，英语...）。 for循环遍历数组，并将用户输入（“ US History”）与数组列表中的字符串进行匹配。 如果它们相等，则返回找到它的索引。 否则，它将继续for循环。 该方法返回一个int，但是在最后一个括号中仍然出现错误。 请帮忙！

 public static int findNumber(String course, int currentQuestion) {
    String newCourse = course.toLowerCase();

    if (RateDriver.levelText.equals("math")) {
      for (int i = 0; i < RateSurvey.math.length-1;i++) {
        if (newCourse.equals(RateSurvey.math[i])) return survey[currentQuestion][i];
      }
      return 100;
    }

    else if (RateDriver.levelText.equals("science")) {
      for (int i = 0; i < RateSurvey.science.length-1;i++) {
        if (newCourse.equals(RateSurvey.science[i])) return survey[currentQuestion][i];

      }
      return 100;
    }
    else if (RateDriver.levelText.equals("english")) {
      for (int i = 0; i < RateSurvey.english.length-1;i++) {
        if (newCourse.equals(RateSurvey.english[i])) return survey[currentQuestion][i];

      }
      return 100;
    }
    else if (RateDriver.levelText.equals("social studies")) {
      for (int i = 0; i < RateSurvey.social.length-1;i++) {
        if (newCourse.equals(RateSurvey.social[i]))  return survey[currentQuestion][i];
      }
    }
    else if (RateDriver.levelText.equals("art")) {
      for (int i = 0; i < RateSurvey.art.length-1;i++) {
        if (newCourse.equals(RateSurvey.art[i])) return survey[currentQuestion][i];
      }
      return 100;
    }
    else if (RateDriver.levelText.equals("pe")) {
      for (int i = 0; i < RateSurvey.pe.length-1;i++) {
        if (newCourse.equals(RateSurvey.pe[i])) return survey[currentQuestion][i];
      }
    }
    else if (RateDriver.levelText.equals("chinese")) {
      for (int i = 0; i < RateSurvey.chinese.length-1;i++) {
        if (newCourse.equals(RateSurvey.chinese[i])) return survey[currentQuestion][i];
      }
    }
    else if (RateDriver.levelText.equals("japanese")) {
      for (int i = 0; i < RateSurvey.japanese.length-1;i++) {
        if (newCourse.equals(RateSurvey.japanese[i])) return survey[currentQuestion][i];
      }
      return 100;
    }
    else if (RateDriver.levelText.equals("french")) {
      for (int i = 0; i < RateSurvey.french.length-1;i++) {
        if (newCourse.equals(RateSurvey.french[i])) return survey[currentQuestion][i];
      }
      return 100;
    }
    else if (RateDriver.levelText.equals("spanish")) {
      for (int i = 0; i < RateSurvey.spanish.length-1;i++) {
        if (newCourse.equals(RateSurvey.spanish[i])) return survey[currentQuestion][i];
      }
      return 100;
    }
    else if (RateDriver.levelText.equals("hawaiian")) {
      for (int i = 0; i < RateSurvey.hawaiian.length-1;i++) {
        if (newCourse.equals(RateSurvey.hawaiian[i])) return survey[currentQuestion][i];
      }
      return 100;
    }
    else return 100;

  **}** // this is where I get the error

Answer 1

如果for循环中未返回任何内容，则代码的某些部分将不会返回任何内容，例如：

else if (RateDriver.levelText.equals("social studies")) {
  for (int i = 0; i < RateSurvey.social.length-1;i++) {
    if (newCourse.equals(RateSurvey.social[i]))  return survey[currentQuestion][i];
  }
}

因此，如果程序到达了代码的这一部分，并且最终没有返回survey[currentQuestion][i] ，那么它将跳至if-else链的末尾，并且不返回任何内容。 您应该将它们更改为以下内容：

else if (RateDriver.levelText.equals("social studies")) {
  for (int i = 0; i < RateSurvey.social.length-1;i++) {
    if (newCourse.equals(RateSurvey.social[i]))  return survey[currentQuestion][i];
  }
  return 100;
}

Answer 2

只需在最后一次return 100;之前删除else return 100; 这意味着，对于所有无法通过巨大的if语句处理的情况，都会发生这种情况。 可能是同一回事，但这只是使代码更清晰。

Answer 3

您需要在一个会引起错误的托架之后添加一个额外的托架。

以下没有任何编译错误：

public static int findNumber(String course, int currentQuestion) {
            String newCourse = course.toLowerCase();

            if (RateDriver.levelText.equals("math")) {
              for (int i = 0; i < RateSurvey.math.length-1;i++) {
                if (newCourse.equals(RateSurvey.math[i])) return survey[currentQuestion][i];
              }
              return 100;
            }

            else if (RateDriver.levelText.equals("science")) {
              for (int i = 0; i < RateSurvey.science.length-1;i++) {
                if (newCourse.equals(RateSurvey.science[i])) return survey[currentQuestion][i];

              }
              return 100;
            }
            else if (RateDriver.levelText.equals("english")) {
              for (int i = 0; i < RateSurvey.english.length-1;i++) {
                if (newCourse.equals(RateSurvey.english[i])) return survey[currentQuestion][i];

              }
              return 100;
            }
            else if (RateDriver.levelText.equals("social studies")) {
              for (int i = 0; i < RateSurvey.social.length-1;i++) {
                if (newCourse.equals(RateSurvey.social[i]))  return survey[currentQuestion][i];
              }
            }
            else if (RateDriver.levelText.equals("art")) {
              for (int i = 0; i < RateSurvey.art.length-1;i++) {
                if (newCourse.equals(RateSurvey.art[i])) return survey[currentQuestion][i];
              }
              return 100;
            }
            else if (RateDriver.levelText.equals("pe")) {
              for (int i = 0; i < RateSurvey.pe.length-1;i++) {
                if (newCourse.equals(RateSurvey.pe[i])) return survey[currentQuestion][i];
              }
            }
            else if (RateDriver.levelText.equals("chinese")) {
              for (int i = 0; i < RateSurvey.chinese.length-1;i++) {
                if (newCourse.equals(RateSurvey.chinese[i])) return survey[currentQuestion][i];
              }
            }
            else if (RateDriver.levelText.equals("japanese")) {
              for (int i = 0; i < RateSurvey.japanese.length-1;i++) {
                if (newCourse.equals(RateSurvey.japanese[i])) return survey[currentQuestion][i];
              }
              return 100;
            }
            else if (RateDriver.levelText.equals("french")) {
              for (int i = 0; i < RateSurvey.french.length-1;i++) {
                if (newCourse.equals(RateSurvey.french[i])) return survey[currentQuestion][i];
              }
              return 100;
            }
            else if (RateDriver.levelText.equals("spanish")) {
              for (int i = 0; i < RateSurvey.spanish.length-1;i++) {
                if (newCourse.equals(RateSurvey.spanish[i])) return survey[currentQuestion][i];
              }
              return 100;
            }
            else if (RateDriver.levelText.equals("hawaiian")) {
              for (int i = 0; i < RateSurvey.hawaiian.length-1;i++) {
                if (newCourse.equals(RateSurvey.hawaiian[i])) return survey[currentQuestion][i];
              }
              return 100;
            }
            else return 100;

          }
        } //ADDED