Question

Java里面对ArrayList 里面的类的对象进行排序应该如何实现？ 现在要求对Car里面的location进行排序。

public class Car {
private String size;
public void setSize(String size){
this.size=size;
}
public String getSize(){
return size;
}

private String location;
public void setLocation(String location){
this.location=location;
}
public String getLocation(){
return location;
}
public String toString() {
return "Car assigned "+location+" "+size;
}
}
Tester 里面是这么读取，存储carlist的。
Scanner in = new Scanner(System.in);
System.out.println("Enter Car info:");
String readstring =in.nextLine();
System.out.println("\n");
String[] readinfo = readstring.split(" ");

int i=0;
int j = 0;
while(in.hasNextLine()&&readinfo[0].equals("Car"))//Case: when scan the first arg[0] is "Car"
{ //store each car's information with corresponding size and location into list
String size = readinfo[1];
String location = readinfo[2];
Car car1 = new Car();
car1.setSize(size);
car1.setLocation(location);
carlist.add(car1);
car1= (Car)carlist.get(i);
System.out.println(car1);
readstring =in.nextLine();
readinfo = readstring.split(" ");
i++;
}

Answer 1

所有car存放在carlist中是吧，存放完成之后再写下面这段代码，对集合排序：
Collections.sort(carlist, new Comparator<Car>() {
@Override
public int compare(Car c1, Car c2) {
return c1.getLocation().compareTo(c2.getLocation());
}
});

Answer 2

重载equal方法上头的已经给出了方法！

Answer 3

实现Comparable接口，并且重写compareTo方法

Answer 4

重载EQUAL方法