---
title: Java常用代码块
date: 2020-10-28
tags: Java
comments: false
cover: https://static.jqwei.com/blog/img/IMG_3461.PNG
categories: 运维工具
---

## java常用代码块

### map 根据Key排序 .

``` java 
    /**
     * map 按 key 升序排序
     *
     * @param map
     * @return
     */
    private static Map<String, Object> sortByKey(Map<String, Object> map) {
        Map<String, Object> result = new LinkedHashMap<>(map.size());
        map.entrySet().stream()
                .sorted(Map.Entry.comparingByKey())
                .forEachOrdered(e -> result.put(e.getKey(), e.getValue()));
        return result;
    }
```

### list 对象根据某个字段分组 .

``` java

    Map<Object,List<Object>> map = demoList.stream().collect(Collectors.groupingBy(Object::getAttr));

```

### list 用stream进行排序 .

``` java

    //根据单个属性排序
    List<String> stortList = list.stream().sorted().collect(Collectors.toList());
    //根据对象某个属性排序
    List<Object> sortList = objectList.stream().sorted(Comparator.comparing(Object::getAttr).reversed()).collect(Collectors.toList());

```