我希望根据ArrayList对<String,int>类型int进行排序。
所以，我的变量是var<String,int>
India 2
Pakistan 3
USA 1
输出变为：
USA 1
India 2
Pakistan 3
我很困惑它如何与int一起使用。 Collections.sort(var)无效。
答案 0 :(得分：4)
您不能使用
类型的ArrayList <String, int>
如果要保存String和int，可以使用字段名称和等级创建一个CountryInfo类。然后创建
ArrayList<CountryInfo> list =new ArrayList<CountryInfo>();
然后你可以使用
Collections.sort(list, <Comparator>)
答案 1 :(得分：0)
这不是ArrayList。在Stead中使用TreeMap。
Map<String, Integer> countryInfo = new TreeMap<String,Integer>();
这样它会自动排序
答案 2 :(得分：0)
ArrayList是一种对象的集合。它不像地图可以采取两个输入。
<强> 1。使用包含Key和Map的TreeMap，并按键或
自动排序<强> 2。使用未排序的地图并使用比较器排序 - 请参阅Sort a Map<Key, Value> by values (Java) 或
第3。使用带比较器的自定义类的arraylist。
-
1）使用TreeMap
树图是红黑树的一种实现方式。请参阅：http://docs.oracle.com/javase/1.5.0/docs/api/java/util/TreeMap.html
TreeMap<Integer,String> countries = new TreeMap<Integer,String>();
countries.put(2, "India");
countries.put(1, "USA");
countries.put(3, "Pakistan");
Iterator<Entry<Integer, String>> it = countries.entrySet().iterator();
Entry<Integer, String> entry;
while(it.hasNext())
{
entry = it.next();
System.out.println(entry.getValue() + " " + entry.getKey());
}
这就产生了：
USA 1
India 2
Pakistan 3
-
2）使用未排序的地图并使用比较器进行排序 请参阅：Sort a Map<Key, Value> by values (Java)，因为答案很清楚。
- 3）使用带有国家/地区类的ArrayList
为了支持您的示例，您需要创建一个Country类。 您需要执行以下操作：
创建一个自定义比较器，您将为其提供Collection.sort调用。
import java.util.ArrayList; import java.util.Collections; import java.util.InputMismatchException; import java.util.Iterator;
公共类CountrySortExample {
public static void main(String[] args) {
new CountrySortExample();
}
public ArrayList<Country> countries = new ArrayList<Country>();
public CountrySortExample()
{
countries.add(new Country("India",2));
countries.add(new Country("Pakistan",3));
countries.add(new Country("USA",1));
Collections.sort(countries);
Iterator<Country> it = countries.iterator();
Country count;
while(it.hasNext())
{
count = it.next();
System.out.println(count.CountryName + " " + count.CountryIndex);
}
}
class Country implements Comparable
{
public String CountryName;
public int CountryIndex;
public Country(String CountryName,int CountryIndex )
{
this.CountryName = CountryName;
this.CountryIndex = CountryIndex;
}
@Override
public int compareTo(Object o) {
if(! (o instanceof Country))
throw new InputMismatchException("Country is expected");
Country other = (Country)o;
if(other.CountryIndex > CountryIndex)
return -1;
else if(other.CountryIndex == CountryIndex)
return 0;
else return 1;
}
}
}
有关详细信息，请访问：http://www.mkyong.com/java/java-object-sorting-example-comparable-and-comparator/
答案 3 :(得分：0)
你可以排序 使用Collections.sort（list，Comparator implementation）
在实现中（这里我使用了匿名实现）覆盖比较方法
你在哪里 获取每个字符串的最后一个字符转换为字符串并比较它们ArrayList<String> a=new ArrayList<String>();
a.add("India 2");
a.add("Pakistan 3");
a.add("USA 1");
Collections.sort(a, new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
Integer i=Integer.valueOf(o1.substring((o1.length() -1),o1.length()));
Integer j=Integer.valueOf(o2.substring((o2.length() -1),o2.length()));
return i.compareTo(j);
}
});
你可以乐观代码
答案 4 :(得分：0)
如果您想要以多种方式排序对象，则为要执行的每种排序类型定义Comparator类。
使用OP提供的示例，这是定义对象和比较器的一种方法。
这是一个测试结果：
CountryRating [name=India, rating=2]
CountryRating [name=Pakistan, rating=3]
CountryRating [name=USA, rating=1]
CountryRating [name=USA, rating=1]
CountryRating [name=India, rating=2]
CountryRating [name=Pakistan, rating=3]
以下是示例代码：
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class CountryRating {
private String name;
private int rating;
public CountryRating(String name, int rating) {
this.name = name;
this.rating = rating;
}
public String getName() {
return name;
}
public int getRating() {
return rating;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("CountryRating [name=");
builder.append(name);
builder.append(", rating=");
builder.append(rating);
builder.append("]");
return builder.toString();
}
public static void main(String[] args) {
List<CountryRating> list = new ArrayList<CountryRating>();
CountryRating cr1 = new CountryRating("USA", 1);
CountryRating cr2 = new CountryRating("India", 2);
CountryRating cr3 = new CountryRating("Pakistan", 3);
list.add(cr1);
list.add(cr2);
list.add(cr3);
Collections.sort(list, new CountrySort());
printList(list);
System.out.println(" ");
Collections.sort(list, new RatingSort());
printList(list);
}
private static void printList(List<CountryRating> list) {
for (int i = 0; i < list.size(); i++) {
System.out.println(list.get(i));
}
}
}
class CountrySort implements Comparator<CountryRating> {
@Override
public int compare(CountryRating cr1, CountryRating cr2) {
return cr1.getName().compareTo(cr2.getName());
}
}
class RatingSort implements Comparator<CountryRating> {
@Override
public int compare(CountryRating cr1, CountryRating cr2) {
return cr1.getRating() - cr2.getRating();
}
}
答案 5 :(得分：0)
我创建了一个示例，您可以对ArrayList进行排序，即使它包含对象。你可以通读它，看看它是否有帮助。
我已经完成了两个课程和一个测试课程：
头等舱是国家：
public class Country {
private String countryName;
private int number;
public Country(String countryName, int number){
this.countryName = countryName;
this.number = number;
}
public String getCountryName(){
return countryName;
}
public void setCountryName(String newCountryName){
countryName = newCountryName;
}
public int getNumber(){
return number;
}
public void setNumber(int newNumber){
number = newNumber;
}
public String toString(){
return getCountryName() + getNumber();
}
}
下一课是方法：
public class Methods {
private Country country;
private ArrayList<Country> overview = new ArrayList<Country>();
private ArrayList<Country> overviewSorted = new ArrayList<Country>();
int [] test;
public void regCountry(String countryname, int numbers){
if(!(countryname == "" && numbers == 0)){
overview.add(new Country(countryname, numbers));
} else {
System.out.println("The input was null");
}
}
public void showRegisteredCountries(){
if(!(overview.size() < 0)){
for(int i = 0; i < overview.size(); i++){
System.out.println("The country: " + overview.get(i).getCountryName() + " has the number: " + overview.get(i).getNumber() + " registered");
}
} else {
System.out.println("There are no country registered");
}
}
public void numbersOverFromArrayList(){
if(!(overview.size() < 0)){
test = new int [overview.size()];
for(int i = 0; i < overview.size(); i++){
test[i] = overview.get(i).getNumber();
}
}
}
public void sortArrayAndCopyItBack(){
if(!(test.length < 0)){
java.util.Arrays.sort(test);
for(int i = 0; i < test.length; i ++){
for(int j = 0; j < overview.size(); j++){
if(test[i] == overview.get(j).getNumber()){
overviewSorted.add(new Country(overview.get(j).getCountryName(), overview.get(j).getNumber()));
}
}
}
}
}
public void showTableSorted(){
if(!(overviewSorted.size() < 0)){
for(int i = 0; i < overviewSorted.size(); i++){
System.out.println("Country name: " + overviewSorted.get(i).getCountryName() + " with number: " + overviewSorted.get(i).getNumber());
}
} else {
System.out.println("There are non countrys in table that is sorted");
}
}
}
接下来是测试类：
public class test2 {
public static void main(String [] args){
Methods methodes = new Methods();
for(int i = 0; i < 4; i++){
String inCountry = JOptionPane.showInputDialog("Country:");
String inNumber = JOptionPane.showInputDialog("number:");
String country = inCountry;
int number = Integer.parseInt(inNumber);
methodes.regCountry(country, number);
}
methodes.showRegisteredCountries();
methodes.numbersOverFromArrayList();
methodes.sortArrayAndCopyItBack();
methodes.showTableSorted();
}
}
我的输出：
The country: Norway has the number: 5 registered
The country: Sweden has the number: 2 registered
The country: Denmark has the number: 9 registered
The country: Finland has the number: 7 registered
Country name: Sweden with number: 2
Country name: Norway with number: 5
Country name: Finland with number: 7
Country name: Denmark with number: 9