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:(上面一行)绑定不匹配:类型MyUtil的通用方法bubbleSort(List,List)不适用于参数(ArrayList,ArrayList)。推断类型Country不是有界参数&gt; 的有效替代 }
//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;
}
}
}
答案 0 :(得分:5)
问题在于您已在行
中指定public static <E extends Comparable<E>>void bubbleSort(List<E> list, List choice)
E
必须延伸Comparable<E>
而Country
则不会。为了使其编译,您必须更改
public class Country {
到
public class Country implements Comparable<Country> {
你还必须实施
public int compareTo(Country c) {}
但这样做不会让您灵活地按多个不同的维度进行排序。