我正在尝试对代表卡牌值的字符串的ArrayList进行排序。因此,有些卡牌包含字母(“King”),而有些卡牌仅包含数字的字符串(“7”)。我知道要使用Collections.sort,但它只能对包含字母的字符串进行排序。如何使ArrayList按数字和字母顺序排序?
编辑:抱歉,当我查看排序时可能没有注意到。排序是正确的,我可能只是被10在2之前的事实所迷惑了。谢谢
编辑:抱歉,当我查看排序时可能没有注意到。排序是正确的,我可能只是被10在2之前的事实所迷惑了。谢谢
不会,Collections.sort
会对所有元素进行排序,使用Unicode字典序比较,因为这就是String.compareTo
的行为。"7"会排在"King"之前,"10"会排在"2"之前。
["7", "Queen", "9", "6"]
,您希望在排序完成后它看起来像["Queen", "9", "7", "6"]
(或按相反顺序排列)。class Card {
private final String name;
private final int value;
...
//constructor and getters
}
Card six = new Card("6", 6);
Card ten = new Card("10", 10);
Card queen = new Card("Queen", 12);
此后,使用字段value
而不是卡片名称来进行所有与卡片相关的操作(特别是排序)将变得更加容易。
<nitpick>
通常作为一种惯例,纸牌也会有“花色”。 </nitpick>
- fmark正如@Jon Skeet所说,内置的sort(排序)将基于Unicode值进行比较。 你需要编写自己的排序方法。
只要你在编写自己的代码,我可以建议一个枚举吗?一副牌是枚举使用的典型示例之一。简而言之,您可以为一组事物声明自己的排序顺序; 如果您想要,您甚至可以使黑桃皇后胜过方块皇后。请查看Sun的教程here。
import java.util.*;
class Sort {
public static void main( String [] args ) {
List list = Arrays.asList("Kings","7", "Abcd", "3.1416");
Collections.sort( list );
System.out.println( list );
}
}
打印
$ java Sort
[3.1416, 7, Abcd, Kings]
这是你需要的吗?
编辑
假设(猜测)你需要对一副牌进行排序,其中既有数字又有“字母”(J、Q、K、A),你可以尝试使用自定义比较器。
这里有一个考虑将数字“作为数字”和其余部分作为字符串的比较器,因此“10”在“2”之后但在“Kings”之前。
import java.util.*;
class Sort {
public static void main( String [] args ) {
List<String> list = Arrays.asList("Kings","7", "Queen", "3", "10", "A", "2", "8", "Joker");
Collections.sort( list , new Comparator<String>(){
public int compare( String a, String b ){
// if both are numbers
if( a.matches("\\d+") && b.matches("\\d+")) {
return new Integer( a ) - new Integer( b );
}
// else, compare normally.
return a.compareTo( b );
}
});
System.out.println( list );
}
}
$ java Sort
[2, 3, 7, 8, 10, A, Joker, Kings, Queen]
class Card implements Comparable<Card> {
public int compareTo( Card other ) {
// add custom logic to compare one card with other
}
}
Sort将根据您的字符集对所有内容进行排序。换句话说,在字典顺序中,所有数字都将排在字母之前。例如,十进制数以“.”开头,并且在字典顺序上是无序的。
如果您想更改此设置,请创建Comparator对象。然后,您可以按任何顺序放置项目。
例如,这将按数字顺序和词汇顺序对单词进行排序:
class CardComparator extends Object implements Comparator{
public int compare(Object a, Object b){
try{
double d1=Double.valueOf(a.toString());
try{
double d2=Double.valueOf(b.toString());
return (d2>d1)?1:-1; // both numeric
}catch(NumberFormatException e){ // a is numeric but b isn't
return 1;
}
}catch(NumberFormatException e){
try{
double d2=Double.valueOf(b.toString());
return -1; // a is nonnumeric but b is
}catch(NumberFormatException e){ // both nonnumeric
return a.toString().compareTo(b.toString);
}
}
}
}
Comparator comparator=new CardComparator();
Collections.sort(cards, comparator);
注意:未经测试!
Sharing an example where I have created two comparator for Lexicographical order, one for Integers and other for String
Note: String by default support Lexicographical order
import java.util.*;
public class ArrayListLexicographicalSort {
public static void main(String[] args) {
//Comparator for Lexicographical order for Integer
Comparator<Integer> comparator = (i,j)->ArrayListLexicographicalSort.lexicographicalSort(i,j);
//Comparator for Lexicographical order for String
Comparator<String> stringComparator = (i,j)->i.compareTo(j);
//list of integers
List<Integer> integerList = Arrays.asList(101,11,2,100,10);
System.out.println(integerList);
//o/p->[101, 11, 2, 100, 10]
//creating a treeset with Lexicographical sort order for Integer
TreeSet<Integer> integerTreeSet = new TreeSet<>(comparator);
integerTreeSet.addAll(integerList);
//resultant Lexicographical order for integers
System.out.println(integerTreeSet);
//o/p->[10, 100, 101, 11, 2]
//list of Strings
List<String> stringList = Arrays.asList("Abhinav","Kumar","Aabhinav","101","100","2");
System.out.println(stringList);
//o/p->[Abhinav, Kumar, Aabhinav, 101, 100, 2]
//creating a treeset with Lexicographical sort order for String
TreeSet<String> stringTreeSet = new TreeSet<>(stringComparator);
stringTreeSet.addAll(stringList);
//resultant Lexicographical order for strings
System.out.println(stringTreeSet);
//o/p->[100, 101, 2, Aabhinav, Abhinav, Kumar]
}
// method to compare two integer lexicographically
private static int lexicographicalSort(long input1, long input2){
// -ve means input1 is smaller
// +ve means input1 is larger
// 0 means input1 and input2 are same
long inp1 = input1;
long inp2 = input2;
int input1Length = 1;
int input2Length = 1;
while(inp1/10>0){
input1Length++;
inp1 = inp1/10;
}
while(inp2/10>0){
input2Length++;
inp2 = inp2/10;
}
int[] inArr1 = new int[input1Length];
int[] inArr2 = new int[input2Length];
inp1 = input1;
inp2 = input2;
int min = Math.min(input1Length,input2Length);
while(inp1/10>0){
inArr1[--input1Length] = (int)inp1%10;
inp1 = inp1/10;
}
inArr1[--input1Length] = (int)inp1;
while(inp2/10>0){
inArr2[--input2Length] = (int)inp2%10;
inp2 = inp2/10;
}
inArr2[--input2Length] = (int)inp2;
int k = 0;
while(k<min){
if( inArr1[k] != inArr2[k]){
return inArr1[k]-inArr2[k];
}
k++;
}
return inArr1.length-inArr2.length;
}
}