我有一个实现Comparable接口的类。在这个类中,我需要覆盖compareTo方法,以便按String值对对象进行排序。
如果你向下滚动到底部,我正试图制作我的方法&我需要在main方法中排序一个Courses数组(使用我正在制作的compareTo方法),首先是Department类型,然后是课程编号等,但这需要比较2个字符串。
import java.io.Serializable;
import java.io.*;
import java.util.*;
public class Course implements Comparable<Course>, Serializable {
private String prefix;
private int number;
private String Department;
private String grade;
/**
* Constructs the course with the specified information.
*
* @param prefix the prefix of the course designation
* @param number the number of the course designation
* @param Department the Department of the course
* @param grade the grade received for the course
*/
public Course(String prefix, int number, String Department, String grade)
{
this.prefix = prefix;
this.number = number;
this.Department = Department;
if (grade == null)
this.grade = "";
else
this.grade = grade;
}
/**
* Constructs the course with the specified information, with no grade
* established.
*
* @param prefix the prefix of the course designation
* @param number the number of the course designation
* @param Department the Department of the course
*/
public Course(String prefix, int number, String Department)
{
this(prefix, number, Department, "");
}
public String getPrefix()
{
return prefix;
}
/**
* Returns the number of the course designation.
*
* @return the number of the course designation
*/
public int getNumber()
{
return number;
}
/**
* Returns the Department of this course.
*
* @return the prefix of the course
*/
public String getDepartment()
{
return Department;
}
/**
* Returns the grade for this course.
*
* @return the grade for this course
*/
public String getGrade()
{
return grade;
}
/**
* Sets the grade for this course to the one specified.
*
* @param grade the new grade for the course
*/
public void setGrade(String grade)
{
this.grade = grade;
}
/**
* Returns true if this course has been taken (if a grade has been received).
*
* @return true if this course has been taken and false otherwise
*/
public boolean taken()
{
return !grade.equals("");
}
* Determines if this course is equal to the one specified, based on the
* course designation (prefix and number).
*
* @return true if this course is equal to the parameter
*/
public boolean equals(Object other)
{
boolean result = false;
if (other instanceof Course)
{
Course otherCourse = (Course) other;
if (prefix.equals(otherCourse.getPrefix()) &&
number == otherCourse.getNumber())
result = true;
}
return result;
}
compareTo
功能:
public int compareTo(Course o)
{
if(getDepartment().equals(o.getDepartment()))
{
return 0;
}
else if()
{
return -1;
}
else
{
return 1;
}
}
/**
* Creates and returns a string representation of this course.
*
* @return a string representation of the course
*/
public String toString()
{
String result = prefix + " " + number + ": " + Department;
if (!grade.equals(""))
result += " [" + grade + "]";
return result;
}
}
到目前为止的主要课程:
import java.util.*;
import java.lang.*;
import java.math.*;
import java.io.*;
import java.*;
public class StackCourse
{
public static void main(String[] args)
{
Course a = new Course("EEE", 230, "Engineering");
Course b = new Course("MAT", 150, "Liberal Arts");
Course c = new Course("PHY", 150, "Liberal Arts");
Course d = new Course("PHI", 304, "Liberal Arts");
Course e = new Course("ECN", 214, "W.P. Carey");
Course f = new Course("EEE", 120, "Engineering");
Course[] courses = {a,b,c,d,e,f};
for(int i=0; i<courses.length; i++)
System.out.println(courses[i].getDepartment());
}
}
答案 0 :(得分:2)
public int compareTo(Course o)
{
if(getDepartment().compareTo(o.getDepartment()) ==0){
if(getNumber() < o.getNumber()) return -1;
else if(getNumber() > o.getNumber()) return 1;
else return 0;
}
return getDepartment().compareTo(o.getDepartment());
}
输出:
答案 1 :(得分:1)
如果我关注你的问题,我相信你想要这样的东西
public int compareTo(Course o)
{
int a = getDepartment().compareTo(o.getDepartment());
if(a != 0)
{
return a;
}
return Integer.valueOf(getNumber()).compareTo(o.getNumber());
}
注意:您可以在比较的字段不是0
时返回,因为这些字段不相等。
答案 2 :(得分:0)
只需使用String的内置compareTo
方法:
@Override
public int compareTo(Course o) {
return this.Department.compareTo(o.Department);
}