Java 使用 Map 集合统计投票人数
package com. zhong. mapdemo. map ;
import javax. swing. plaf. synth. SynthOptionPaneUI ;
import java. util. ArrayList ;
import java. util. HashMap ;
import java. util. Map ;
public class MapCountPeopleNumber {
public static void main ( String [ ] args) {
ArrayList < String > arrayList = new ArrayList < > ( ) ;
arrayList. add ( "A" ) ;
arrayList. add ( "B" ) ;
arrayList. add ( "C" ) ;
arrayList. add ( "A" ) ;
arrayList. add ( "D" ) ;
arrayList. add ( "B" ) ;
arrayList. add ( "A" ) ;
arrayList. add ( "C" ) ;
arrayList. add ( "C" ) ;
arrayList. add ( "A" ) ;
arrayList. add ( "D" ) ;
arrayList. add ( "B" ) ;
arrayList. add ( "A" ) ;
arrayList. add ( "C" ) ;
System . out. println ( "-------------原始投票情况-------------" ) ;
System . out. println ( arrayList) ;
System . out. println ( "-------------统计投票情况-------------" ) ;
Map < String , Integer > hashMap = new HashMap < > ( ) ;
arrayList. forEach ( x -> {
Integer i = hashMap. containsKey ( x) ? hashMap. put ( x, hashMap. get ( x) + 1 ) : hashMap. put ( x, 1 ) ;
} ) ;
System . out. println ( hashMap) ;
}
}