Collectors示例分享

package com.java265;
 
import java.util.Arrays;
import java.util.list;
import java.util.stream.Collectors;
 
public class GroupingTransaction {
    public static void main(String[] args) {
        List<Transaction> transactions = Arrays.asList(
                new Transaction(Currency.EUR, 800.0),
                new Transaction(Currency.USD, 1200.0),
                new Transaction(Currency.GBP, 100.0),
                new Transaction(Currency.EUR, 6300.0),
                new Transaction(Currency.JPY, 2200.0),
                new Transaction(Currency.CHF, 9000.0),
                new Transaction(Currency.EUR, 3200.0),
                new Transaction(Currency.USD, 2200.0),
                new Transaction(Currency.CHF, 600.0),
                new Transaction(Currency.GBP, 700.0),
                new Transaction(Currency.USD, 600.0),
                new Transaction(Currency.JPY, 1700.0),
                new Transaction(Currency.EUR, 2800.0) );
        transactions.stream()
                .collect(Collectors.groupingBy(Transaction::getCurrency))
                .forEach((c,list)->System.out.println(c+":"+list));
    }
}