为什么老是抛出异常 ,那儿错了么???
import java.util.*;
import java.util.Collection;
import java.util.TreeSet;public class as implements Comparable{
public static void main(String[] agrs){
Collection<Student> treeset = new TreeSet<Student>();
Student s1=new Student(12345,"John","Smith");
Student s2=new Student(23456,"Jane","Smith");
Student s3=new Student(34567,"Adam","Smith");
Student s4=new Student(45678,"Tom","Jones");
treeset.add(s1);
treeset.add(s2);
treeset.add(s3);
treeset.add(s4);
for(Student student:treeset){
System.out.println(student.getFullname());
}
}
//实现Comparable接口的方法
public int compareTo(Object o){
assert((o instanceof Student)&&(o!=null));
Student s=(Student)o;
int relativeValue=s.LastName.compareTo(s.getLastName());
if(relativeValue==0){
relativeValue=s.FirstName.compareTo(s.getFirstName());
}
return relativeValue;
}}
//student类public class Student {
private long ID;
String FirstName;
String LastName;
public Student(long id,String fn,String ln){
ID=id;
FirstName=fn;
LastName=ln;
}
public String getFirstName(){
return FirstName;
}
public String getLastName(){
return LastName;
}
public String getFullname(){
return FirstName+" "+LastName;
}
}
import java.util.*;
import java.util.Collection;
import java.util.TreeSet;public class as implements Comparable{
public static void main(String[] agrs){
Collection<Student> treeset = new TreeSet<Student>();
Student s1=new Student(12345,"John","Smith");
Student s2=new Student(23456,"Jane","Smith");
Student s3=new Student(34567,"Adam","Smith");
Student s4=new Student(45678,"Tom","Jones");
treeset.add(s1);
treeset.add(s2);
treeset.add(s3);
treeset.add(s4);
for(Student student:treeset){
System.out.println(student.getFullname());
}
}
//实现Comparable接口的方法
public int compareTo(Object o){
assert((o instanceof Student)&&(o!=null));
Student s=(Student)o;
int relativeValue=s.LastName.compareTo(s.getLastName());
if(relativeValue==0){
relativeValue=s.FirstName.compareTo(s.getFirstName());
}
return relativeValue;
}}
//student类public class Student {
private long ID;
String FirstName;
String LastName;
public Student(long id,String fn,String ln){
ID=id;
FirstName=fn;
LastName=ln;
}
public String getFirstName(){
return FirstName;
}
public String getLastName(){
return LastName;
}
public String getFullname(){
return FirstName+" "+LastName;
}
}
import java.util.Collection;
import java.util.TreeSet;public class as { public static void main(String[] agrs) { Collection<Student> treeset = new TreeSet<Student>();
Student s1 = new Student(12345, "John", "Smith");
Student s2 = new Student(23456, "Jane", "Smith");
Student s3 = new Student(34567, "Adam", "Smith");
Student s4 = new Student(45678, "Tom", "Jones");
treeset.add(s1);
treeset.add(s2);
treeset.add(s3);
treeset.add(s4);
for (Student student : treeset) {
System.out.println(student.getFullname());
}
}}// student类class Student implements Comparable {
private long ID;
String FirstName;
String LastName; public Student(long id, String fn, String ln) {
ID = id;
FirstName = fn;
LastName = ln;
} public String getFirstName() {
return FirstName;
} public String getLastName() {
return LastName;
} public String getFullname() {
return FirstName + " " + LastName;
} // 实现Comparable接口的方法
public int compareTo(Object o) {
assert ((o instanceof Student) && (o != null)); Student s = (Student) o;
int relativeValue = this.LastName.compareTo(s.getLastName());
if (relativeValue == 0) {
relativeValue = this.FirstName.compareTo(s.getFirstName());
} return relativeValue;
}
}