使用Arrays.sort（）对自定义的entity按指定属性进行排序。
使用Arrays.sort（）对自定义的entity按指定属性进行排序。
若想达到上面功能，自定义entity必须实现Comparable接口，然后重写compareTo()方法。
public class Employee implements Comparable{
private String name;
private int age;
public Employee(String n,int a){
this.name = n;
this.age = a;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public int compareTo(Employee o) {
// TODO Auto-generated method stub
int i = 0;
if(this.age > o.age){//这里比较的什么，sort()方法就按什么从小到大排序
i = 1;
}else if(this.age < o.age){
i = -1;
}
return i;
}
} public class ArraysSortTest {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Employee []employees = new Employee[3];
employees[0] = new Employee("yuying",34);
employees[1] = new Employee("hanying",25);
employees[2] = new Employee("laoyang",26);
Arrays.sort(employees);
for(Employee e:employees){
System.out.println(e.getName() + "----" + e.getAge());
}
}
}也可以这样：
public class ArraysSortTest {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Employee []employees = new Employee[4];
employees[0] = new Employee("yuying",34);
employees[1] = new Employee("hanying",25);
employees[2] = new Employee("laoyang",26);
employees[3] = new Employee("Dr.Cao",53);
// Arrays.sort(employees);
List e_list = Arrays.asList(employees);
Collections.sort(e_list);
for(Employee e:employees){
System.out.println(e.getName() + "----" + e.getAge());
}
}
} 附加一道Java面试题：
Comparable和Comparator接口是干什么的？列出它们的区别。
Java提供了只包含一个compareTo()方法的Comparable接口。这个方法可以个给两个对象排序。具体来说，它返回负数，0，正数来表明输入对象小于，等于，大于已经存在的对象。
Java提供了包含compare()和equals()两个方法的Comparator接口。compare()方法用来给两个输入参数排序，返回负数，0，正数表明第一个参数是小于，等于，大于第二个参数。equals()方法需要一个对象作为参数，它用来决定输入参数是否和comparator相等。只有当输入参数也是一个comparator并且输入参数和当前comparator的排序结果是相同的时候，这个方法才返回true。
与Comparator的区别
Comparator位于包java.util下，而Comparable位于包java.lang下，Comparable接口将比较代码嵌入自身类中，而后者在一个独立的类中实现比较。 如果类的设计师没有考虑到Compare的问题而没有实现Comparable接口，可以通过 Comparator来实现比较算法进行排序，并且为了使用不同的排序标准做准备，比如：升序、降序。
public class Contractor {
private String name;
private double salary;
public Contractor(String n,double s){
this.name = n;
this.salary = s;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
@Override
public String toString(){
return this.name + "----" + this.salary;
}
}专门实现一个比较器，这里按照Contractor实体的salary属性进行比较。
import java.util.Comparator;
public class ContractorComparator implements Comparator{
@Override
public int compare(Contractor o1, Contractor o2) {
// TODO Auto-generated method stub
int i = 0;
if(o1.getSalary() < o2.getSalary()){
i = -1;
}else if(o1.getSalary() > o2.getSalary()){
i = 1;
}
return i;
}
} public class ContractorTest {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Contractor []contractors = new Contractor[4];
contractors[0] = new Contractor("xiaowei",1100.0);
contractors[1] = new Contractor("yuying",920.0);
contractors[2] = new Contractor("mentoryang",1120.0);
contractors[3] = new Contractor("Dr.Cao",5100.0);
List c_list = Arrays.asList(contractors);
ContractorComparator cc = new ContractorComparator();
Collections.sort(c_list,cc);
for(Contractor c:c_list){
System.out.println(c);
}
}
} 也可以这样实现：
public class ContractorTest {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
ContractorComparator cc = new ContractorComparator();
Set c_set = new TreeSet(cc);//这里需要传一个参数，这个参数就是比较器
c_set.add(new Contractor("xiaowei",1100.0));
c_set.add(new Contractor("yuying",920.0));
c_set.add(new Contractor("mentoryang",1120.0));
c_set.add(new Contractor("Dr.Cao",5100.0));
for(Contractor c:c_set){
System.out.println(c);
}
}
}