zoukankan      html  css  js  c++  java
  • Effective Java 50 Avoid strings where other types are more appropriate

    Principle

    • Strings are poor substitutes for other value types. Such as int, float or BigInteger.
    • Strings are poor substitutes for enum types. As discussed in Item 30.
    • Strings are poor substitutes for aggregate types. A better approach is simply to write a class to represent the aggregate, often a private static member class (Item 22).

      // Inappropriate use of string as aggregate type

      String compoundKey = className + "#" + i.next();

         

    • Strings are poor substitutes for capabilities(unforgeable key).

      Client-provided string keys are used to identify each thread-local variable:

         

      // Broken - inappropriate use of string as capability!

      public class ThreadLocal {

      private ThreadLocal() { } // Noninstantiable

      // Sets the current thread's value for the named variable.

      public static void set(String key, Object value);

      // Returns the current thread's value for the named variable.

      public static Object get(String key);

      }

         

      The root cause: the string keys represent a shared global namespace for thread-local variables.

         

      public class ThreadLocal {

      private ThreadLocal() { } // Noninstantiable

      public static class Key { // (Capability)

      Key() { }

      }

      // Generates a unique, unforgeable key

      public static Key getKey() {

      return new Key();

      }

      public static void set(Key key, Object value);

      public static Object get(Key key);

      }

         

      It is a simple, faster and more elegant matter to make this API typesafe by generifying the ThreadLocal class (Item 26):

      public final class ThreadLocal<T> {

      public ThreadLocal() { }

      public void set(T value);

      public T get();

      }

         

      Summary

      Avoid the natural tendency to represent objects as strings when better data types exist or can be written. Used inappropriately, strings are more cumbersome, less flexible, slower, and more error-prone than other types. Types for which strings are commonly misused include primitive types, enums, and aggregate types.

         

  • 相关阅读:
    网站实时信息采集和统计graphite
    内存检查工具Valgrind
    usr/bin/ld: cannot find 错误解决方法和 /etc/ld.so.conf
    通用makefile
    关于/proc/进程idpid/fd ,根据fd来查找连接
    boost enable_shared_from_this
    cdll和windll的差别
    一些项目——空白格式化
    Session笔记
    黑马程序猿_7K面试题之交通灯系统
  • 原文地址:https://www.cnblogs.com/haokaibo/p/avoid-strings-where-other-types-are-more-appropriate.html
Copyright © 2011-2022 走看看