@PostContruct是spring框架的注解，在方法上加该注解会在项目启动的时候执行该方法，也可以理解为在spring容器初始化的时候执行该方法。 @Componentpublic class SettingManager {    @Inject    private SettingService settingService;    @Inject    private SettingItemService settingItemService;    private static SettingManager settingManager;    private Long userId;    private List
      
        settingItems;    @PostConstruct    public void init() {        settingManager = this;    }}
      

 

 

 

map的高级用法

public StatictisDataWrapper(Map
     
      > map) {        this.list = new ArrayList<>();        map.forEach((string, statistics) -> list.add(new StatictisData(string, statistics)));    }
     

map获取不到就设定默认值String metastore = map.getOrDefault("hive.metastore.uris", "");

default的使用

@Target({TYPE,METHOD,FIELD,CONSTRUCTOR})  @Retention(RetentionPolicy.RUNTIME)  public @interface TestA {      String name();      int id() default 0;      Class
     
       gid();  }
     

 stream 聚合:

public Map
     
       aggCount() {        return this.getNotNullValues().stream().collect(Collectors.groupingBy(s -> s, Collectors.counting()));    }
     

 FileUtil的用法

/**     * 文件操作     **/    private static void writeFile(File file, String content) {        try {            FileUtils.writeStringToFile(file, content, "UTF-8");        } catch (IOException e) {            logger.error("Exception:write title file error!", e);        }    }    private static void writeLines(File file, List
     
       lines) {        try {            FileUtils.writeLines(file, "UTF-8", lines);        } catch (IOException e) {            logger.error("Exception:write title file error!", e);        }    }    private static String readFile(File file) {        try {            return FileUtils.readFileToString(file, "UTF-8");        } catch (IOException e) {            logger.error("Exception:read type file error", e);            return "";        }    }    private static List
      
        readLines(File file) {        try {            return FileUtils.readLines(file, "UTF-8");        } catch (IOException e) {            logger.error("Exception:read type file error", e);            return new ArrayList<>();        }    }
      
     

重写借口的方法 public interface ProcessStreamHandler {    void handle(String var1);} ProcessStreamHandler handler = (line) -> {                FileUtil.writeFile(logFile, line + "\r\n", true);            }

ProcessUtil processUtil = new ProcessUtil(handler);

 for用法

for(var5 = sparkAction.getAppArgs().iterator(); var5.hasNext(); launcher = launcher.addAppArgs(new String[]{arg})) {                    arg = (String)var5.next();                }