Question

我正在尝试对数组列表进行冒泡排序，但我一直收到错误bad operand types for binary operator '>'我正在尝试按数字顺序对其进行排序，以获得下面列出的测试分数。我是java的新手，对于该怎么做我很困惑。我很确定整数存储在列表中。

我的代码是：

 public static void sort(){
               int k = 0;
           boolean exchangeMade = true;
           while((k < classroom.size() - 1) &&exchangeMade){
              exchangeMade = false;
              k++;
              for (int j = 0; j < classroom.size() - k; j++)
                  if(classroom.get(j) > classroom.get(j+1)){
                    swap(j, j+1);
                    swap(classroom, j, j+1);
                    exchangeMade = true;
              }
          }

该程序的其余代码是

public class Test {

  private static FileInputStream inFile;
  private static InputStreamReader inReader;
  private static BufferedReader reader;

  private static List<Student> classroom =
      new ArrayList<Student>(); // ArrayList to store the classroom.

  public static void main(String args[]) throws IOException {
    initFile();
    getData();
    System.out.print(classroom); //output of the complete class.
    sort();
    System.out.print(classroom); //output after sorting.
    inFile.close();
  }

  // preparing the file for input

  public static void initFile() throws IOException {

    inFile =
        new FileInputStream(
            "C:\\Users\\clamanna\\Google Drive\\Senior\\AP COMP SCI\\!!VHSJava\\!!APCSDATA\\truefalse.txt");
    inReader = new InputStreamReader(inFile);
    reader = new BufferedReader(inReader);
  }

  //  Separate the id from the answers and store the answers in an array.

  public static void getData() throws IOException {
    String line = reader.readLine(); //Seed

    String[] answerkey = new String[10]; //Store the answer key from the first line of the txt file.

    for (int i = 0;
        i < answerkey.length;
        i++) { // take that line and place each answer in an array.

      answerkey[i] = line.substring(i, i + 1);
    }

    line = reader.readLine(); // read the following line of the txt file.

    while (line != null) // Read and create a student for each line.
    {
      String[] answers = new String[10];
      StringTokenizer strTkn = new StringTokenizer(line);
      String id = strTkn.nextToken();
      String answerline = strTkn.nextToken();

      for (int i = 0; i < answers.length; i++) {

        answers[i] = answerline.substring(i, i + 1);
      }

      Student stu = new Student(id, answers);

      stu.grade(answerkey, answers);

      classroom.add(stu);

      line = reader.readLine(); //updating what is being read
    }
  }
}

Answer 1

>和<等关系型运算符仅定义为int和double等数字基元类型。

您也可以将它们用于等同的盒装类型，例如Integer和Double，因为这些类型可以自动取消装入基元。

要比较对象，您应该使用Comparable.compareTo方法：

classroom.get(j).compareTo(classroom.get(j+1)) > 1

请注意，这需要您的元素实现Comparable界面 - Integer，Double等常见类型，以及String之类的内容（实现Comparable它与词典顺序一致）。

如果您的元素类没有实现Comparable（并且您无法对其进行更改以实现它），则可以使用名为Comparator的interface Comparable<T> { int compare(T a, T b); }“外部”形式，这是一个这样的界面：

compare

您不添加到您想要比较的类的

- 您将此接口实现为单独的类，以便a < b返回负数，零或正数如果您分别考虑a == b，a > b和comparator.compare(classroom.get(j), classroom.get(j + 1)) > 1，请编号。

然后，您将使用：

comparator

其中Comparator<Student>是实现Comparator<? super Student>的类的实例。（实际上，它可以是means= numpy.arange(10) means=pd.DataFrame(means.reshape(5,2)) stds=numpy.arange(10,20) stds=pd.DataFrame(sts.reshape(5,2)) samples={} for i in means.columns: col={} for j in means.index: col[j]=numpy.random.normal(means.ix[j,i],stds.ix[j,i],2) samples[i]=col print(pd.DataFrame(samples)) # 0 1 #0 [0.0760974520154, 3.29439282825] [11.1292510583, 0.318246201796] #1 [-25.4518020981, 19.2176263823] [17.0826945017, 9.36179435872] #2 [14.5402484325, 8.33808246538] [6.96459947914, 26.5552235093] #3 [0.775891790613, -2.09168601369] [2.38723023677, 15.8099942902] #4 [-0.828518484847, 45.4592922652] [26.8088977308, 16.0818556353]，但现在不要担心太多了。

泡泡排序ArrayList时遇到问题

1 个答案: