问您能否使用函数式/函数式编程来对Java 7中的列表进行分组(并按组计算其元素)？

EN

public Map<TypeEnum, Integer> countByGroup(List<TypeEnum> types) {
    Map<TypeEnum, Integer> countedTypes = new HashMap<>();
    for(TypeEnum type : types) {
        if(countedTypes.containsKey(type)) {
            countedTypes.put(type, countedTypes.get(type) + 1);
        } else {
            countedTypes.put(type, 1);
        }
    }
    return countedTypes;
}

Procedure<TypeEnum> count = new Procedure<TypeEnum>() {
public Map<TypeEnum, Integer> countPerType = null;

    @Override
    public void run(TypeEnum type) {
        if(countPerType.containsKey(type)) {
            countPerType.put(type, countPerType.get(type) + 1);
        } else {
            countPerType.put(type, 1);
        }
    }

    public Procedure<TypeEnum> init(Map<TypeEnum, Integer> countPerType) {
        this.countPerType = countPerType;
        return this;
    }
}.init(countPerType); // kudos http://stackoverflow.com/a/12206542/2018047