[转]归约与分组 – 读《Java 8实战》
点击数:5收集器用作高级归约 // 按货币对交易进行分组 Map currencyListMap = getTransactions().stream() .collect(groupingBy(Transaction::getCurrency)); for (Map.Entry entry : currencyListMap.entrySet()) { System.out.println(entry.getKey() + “\t” + entry.getValue().size()); } …