java常用小技巧！

1.判斷集合是否爲空CollectionUtils.isEmpty(list)
2.遍歷map集合list是個集合類

List<Map<String, String>> list = new ArrayList<Map<String, String>>();
    Iterator<Entry<String,String>> iterator = JsonUtils.toObject(substring.trim(), Map.class).entrySet().iterator();
        while(iterator.hasNext()){
            Entry<String, String> entry = iterator.next();
            Map<String, String> map = new HashMap<String, String>();
            map.put("value",entry.getValue());
            map.put("key",entry.getKey());
            list.add(map);
        }

3.去掉屬性下劃線改爲駝峯式

    public static String getPropertyName(String propertyName) {
        propertyName = propertyName.toLowerCase();
        String[] name = propertyName.split("_");
        propertyName = name[0];
        for (int i = 1; i < name.length; i++) {
            propertyName = propertyName + name[i].substring(0,1).toUpperCase() + name[i].substring(1);
        }
        return propertyName;
    }

4.json，object互轉換類用到的包com.fasterxml.jackson.databind.ObjectMapper

private static ObjectMapper mapper = new ObjectMapper();

    /**
     * toJson(把對象轉換成json)<br/>
     */
    public static String toJson(Object value) {
        try {
            return mapper.writeValueAsString(value);
        } catch (Exception e) {
            log.error("轉換json失敗", e);
            throw new RuntimeException("json轉換異常", e);
        }
    }

    /**
     * toObject(把json轉換成對象)<br/>
     */
    public static <T> T toObject(String json, Class<T> clazz) {
        try {
            return mapper.readValue(json, clazz);
        } catch (Exception e) {
            log.error("json轉換對象失敗", e);
            throw new RuntimeException("json轉換對象異常", e);
        }
    }