• 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:
    并发编程---守护进程
    并发编程---Process对象的其他属性或方法
    并发编程---开启进程方式---查看进程pid
    并发编程---操作系统
    ie浏览器的css bug
    链接内的图片与文字如何对齐?
    inline元素特性
    最大流EK算法模板
    数据结构 链式表
    运算表达式 栈应用
  • 原文地址:https://www.cnblogs.com/haokaibo/p/avoid-strings-where-other-types-are-more-appropriate.html
Copyright © 2020-2023  润新知