我有一个查询我开发了一个pojo ..
public class Customer {
int Age;
public Customer(int age, String surname, String forename) {
super();
Age = age;
Surname = surname;
Forename = forename;
}
String Surname,Forename;
public int getAge() {
// TODO Auto-generated method stub
return Age;
}
public String getSurname() {
// TODO Auto-generated method stub
return Surname;
}
public String getForename() {
// TODO Auto-generated method stub
return Surname;
}
public void display()
{
// System.out.println(Forename+"\t"+Surname+"\t"+Age);
System.out.println(Age+"\t"+Forename+"\t"+Surname);
}
}
这是我的收藏班..
class testCustomerComparator
{
public static void main(String... a)
{
Customer customerFirst = new Customer(46,"Alabama", "Christonson");
Customer customerSecond = new Customer(21, "Anna", "Sobek");
Customer customerThird = new Customer(27, "Rafael", "Sobek");
List<Customer> list = new ArrayList<Customer>();
list.add(customerThird);
list.add(customerSecond);
list.add(customerFirst);
}
}
请告诉我如何为这个班级制作计算器，我想制作比较器，以便按年龄排序客户列表，按姓氏排序。之后你想按名字排序。请告知我在比较器中有嵌套条件
好吧，好像有点像...... public class CustomerComparator implements Comparator<Customer> {
@Override
public int compare(Customer c1, Customer c2) {
if (c1.getAge() == c2.getAge()) {
if (c1.getSurname().compareTo(c2.getSurname()) == 0) {
return c1.getForename().compareTo(c2.getForename()) {
} else {
return c1.getSurname().compareTo(c2.getSurname());
}
} else if (c1.getAge() > b2.getAge()) {
return -1;
} else {
return 1;
}
}
但它不起作用请告知
答案 0 :(得分：1)
看起来很像家庭作业。我可以给你一些关于在哪里看的提示。
您有两种选择：
Comparable<Customer> Comparator<Customer>。假设第二个选择，你有两个明确的客户，你必须定义一个类似于这个的方法：
@Override
public int compare(Customer c1, Customer c2)
{
// this method should return 0 if c1.equals(c2),
// should instead return 1 if c1 should come first than c2 and -1 otherwise
}
答案 1 :(得分：0)
public class CustomerComparator implements Comparator<Customer> {
public int compare(Customer c1, Customer c2) {
.... here you have c1 and c2. compare returns -1 if c1 should go before c2,
0 if they are found to be equal, and 1 if c2 should go before c1.
You add the logic to compare c1 and c2 fields as you stated and return the result.
}
}
然后使用Collections.sort使用此比较器对该列表进行排序。
答案 2 :(得分：0)
您可以提供以下代码的帮助。
import java.util.*;
class Customer {
private int age;
private String name;
private String forename;
public Customer(int age, String surname, String forename) {
super();
this.age = age;
this.name = surname;
this.forename = forename;
}
public void setAge(int age) {
this.age = age;
}
public int getAge() {
return this.age;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
public void setForename(String forename) {
this.forename = forename;
}
public String getForename() {
return forename;
}
}
class AgeComparator implements Comparator {
public int compare(Object emp1, Object emp2) {
int emp1Age = ((Customer) emp1).getAge();
int emp2Age = ((Customer) emp2).getAge();
if (emp1Age > emp2Age)
return 1;
else if (emp1Age < emp2Age)
return -1;
else
return 0;
}
}
/*
* The below given comparator compares employees on the basis of their name.
*/
class NameComparator implements Comparator {
public int compare(Object emp1, Object emp2) {
// parameter are of type Object, so we have to downcast it to Employee
// objects
int emp1Age = ((Customer) emp1).getAge();
int emp2Age = ((Customer) emp2).getAge();
if (emp1Age > emp2Age) {
return 1;
} else if (emp1Age < emp2Age) {
String emp1Name = ((Customer) emp1).getName();
String emp2Name = ((Customer) emp2).getName();
// uses compareTo method of String class to compare names of the
// employee
return emp1Name.compareTo(emp2Name);
} else {
return 0;
}
}
}
class CustomerComparator implements Comparator {
public int compare(Object emp1, Object emp2) {
// parameter are of type Object, so we have to downcast it to Employee
// objects
String emp1Name = ((Customer) emp1).getName();
String emp2Name = ((Customer) emp2).getName();
// uses compareTo method of String class to compare names of the
// employee
return emp1Name.compareTo(emp2Name);
}
}
public class JavaComparatorExample {
public static void main(String args[]) {
// Employee array which will hold employees
Customer employee[] = new Customer[3];
// set different attributes of the individual employee.
employee[0] = new Customer(46, "Alabama", "Christonson");
employee[1] = new Customer(21, "Anna", "Sobek");
employee[2] = new Customer(27, "Rafael", "Sobek");
System.out.println("Order of employee before sorting is");
// print array as is.
for (int i = 0; i < employee.length; i++) {
System.out.println("Employee " + (i + 1) + " name :: "
+ employee[i].getName() + ", Age :: "
+ employee[i].getAge());
}
Arrays.sort(employee, new AgeComparator());
System.out
.println("\n\nOrder of employee after sorting by employee age is");
for (int i = 0; i < employee.length; i++) {
System.out.println("Employee " + (i + 1) + " name :: "
+ employee[i].getName() + ", Age :: "
+ employee[i].getAge());
}
// Sorting array on the basis of employee Name by passing NameComparator
Arrays.sort(employee, new NameComparator());
System.out
.println("\n\nOrder of employee after sorting by employee name is");
for (int i = 0; i < employee.length; i++) {
System.out.println("Employee " + (i + 1) + " name :: "
+ employee[i].getName() + ", Age :: "
+ employee[i].getAge());
}
}
}
希望这会对你有所帮助。
修改
查看CustomerComparator班。
答案 3 :(得分：0)
@Override
public int compare(Customer c1, Customer c2) {
int r = Integer.valueOf(c1.getAge()).compareTo(c2.getAge());
if (r != 0) return r;
r = c1.getSurname().compareTo(c2.getSurname());
if (r != 0) return r;
return c1.getForename().compareTo(c2.getForename());
}