public class Main {
public static void main(String[] args) throws FileNotFoundException {
ArrayList<Country> cList = new ArrayList<Country>();
ArrayList choice = new ArrayList();
File inf = new File("src/countrydata.txt");
Scanner scan = new Scanner(inf).useDelimiter("[\t|\n|\r]+");
Scanner s = new Scanner(System.in);
int p = 0;
double g = 0;
while(scan.hasNext()){
cList.add(new Country(scan.next(), scan.nextInt(), scan.nextDouble()));
}
System.out.print("Would you like in sorted my name(n), population(p) or growth(g): ");
String go = s.next();
go = go.toLowerCase();
if(go.equals("n")){
choice.add(go);
}else if(go.equals("p")){
choice.add(p);
}else if(go.equals("g")){
choice.add(g);
}
MyUtil.bubbleSort(cList, choice);
我的错误:(上面的行)绑定不匹配:类型为MyUtil的通用方法bubbleSort(List,List)不适用于参数(ArrayList,ArrayList)。推断出的国家(地区)类型不是有效替代边界参数>
}
//Sort Class
public class MyUtil <E extends Comparable<E>>{
public static <E extends Comparable<E>>void bubbleSort(List<E> list, List choice){
int n = list.size();
boolean swap = true;
while(swap){
swap = false;
for(int i = 0; i < n-1; i++){
if(list.get(i).compareTo(list.get(i+1)) == 1){
swap(list, i, i+1);
swap = true;
}
}
}
}
public static <E extends Comparable<E>>void swap(List<E> list, int i, int j){
E temp = list.get(i);
list.set(i, list.get(j));
list.set(j, temp);
}
}
public class Country {
private String name;
private int population;
private double growth;
public Country(String name, int population, double growth){
this.name = name;
this.population = population;
this.growth = growth;
}
public String getName(){return name;}
public int getPopulation(){return population;}
public double getGrowth(){return growth;}
public String toString(){
return name + ", population of " + population + ", with an anual growth of: " + growth + ".";
}
public int compareTo(Country c, String s){
if(name.substring(0, 1).compareTo(c.getName().substring(0, 1)) > 0){
return -1;
}else if(name.substring(0, 1).compareTo(c.getName().substring(0, 1)) == 0){
return 0;
}else{
return 1;
}
}
public int compareTo(Country c, int p){
if(population < c.getPopulation()){
return -1;
}else if(population == c.getPopulation()){
return 0;
}else{
return 1;
}
}
public int compareTo(Country c, double g){
if(growth < c.getGrowth()){
return -1;
}else if(growth == c.getGrowth()){
return 0;
}else{
return 1;
}
}
}
最佳答案
问题是您已在该行中指定
public static <E extends Comparable<E>>void bubbleSort(List<E> list, List choice)
E
必须扩展Comparable<E>
,而Country
不需要扩展。为了使其编译,您必须进行更改public class Country {
至
public class Country implements Comparable<Country> {
而且您还必须实施
public int compareTo(Country c) {}
但是以这种方式进行操作将无法为您提供按多个不同维度进行排序的灵活性。