在同一个包和目录中找不到符号

Question

我有两个类，既定课程和课程。它们都在同一个包和同一个目录中。

Offering.java:

package assignment02;

public class Offering implements Comparable<Offering> {
    private Course course;
    private int CRN;
    private int semester;

    public Offering(Course course, int CRN, int semester) {
        this.course = course;
        this.CRN = CRN;
        this.semester = semester;
    }

    public int getNumCredits() {
        return course.getNumCredits;
    }

    public int getCRN() {
        return CRN;
    }

    public int getSemester() {
        return semester;
    }

    public int compareTo(Offering other) {
        if(other == null) return - 1;
        return semester - other.semester;
    }
}

Course.java:

package assignment02;

public class Course {
    private String name;
    private String rubric;
    private String number;
    private int numCredits;

    public Course(String name, String rubric, String number, int numCredits) {
        this.name = name;
        this.rubric = rubric;
        this.number = number;
        this.numCredits = numCredits;
    }

    public String getName() {
        return name;
    }

    public String getRubric() {
        return rubric;
    }

    public String getNumber() {
        return number;
    }

    public int getNumCredits() {
        return numCredits;
    }
}

当我尝试编译既定课程时，出现错误：

D:\CS 140\assignment02>javac Offering.java
Offering.java:4: error: cannot find symbol
    private Course course;
            ^
   symbol:   class Course
   location: class Offering

和

Offering.java:8: error: cannot find symbol
    public Offering(Course course, int CRN, int semester) {
                    ^
   symbol:   class Course
   location: class OfferingOffering.java:8: error: cannot find symbol

我知道错误意味着编译器无法对 'Course,' 执行任何操作，但我真的不知道为什么。我也知道它最终会变得非常明显，但我似乎无法弄清楚。任何帮助将不胜感激。

Answer 1

你需要先编译Course.java——Offering.java依赖它，因为你引用了它。另外，

public int getNumCredits() {
    return course.getNumCredits;
}

应该是

public int getNumCredits() {
    return course.getNumCredits();
}

Answer 2

将目录更改为 assignment02 的父目录。然后你应该可以使用

javac assignment02\Course.java assignment02\Offering.java

或

javac assignment02\Course.java 
javac assignment02\Offering.java

甚至

javac assignment02\*.java

编译器正在从您当前目录的 assignment02 包中寻找 Course class（因此当您在 assignment02 目录中时，它是有效地尝试查看 assignment02/assignment02，这显然是不正确的）。

虽然这会解决您当前的问题，但您会收到以下错误：

assignment02\Offering.java:15: cannot find symbol
symbol  : variable getNumCredits
location: class assignment02.Course
    return course.getNumCredits;
                 ^
1 error

需要更正。

Answer 3

您也可以使用“-classpath”参数进行编译，并将其值设置为父目录，如下所示：

javac -classpath .. Offering.java

在同一个包和目录中找不到符号

Cannot find symbol in same package and directory

java

compilation

symbols