Java 示例 - 字符串优化

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  问题描述

  如何优化字符串创建？
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  解决方案

  以下示例使用 String.intern() 方法优化字符串创建。

  
  public class StringOptimization {
     public static void main(String[] args) {
        String variables[] = new String[50000];     
        for( int i = 0; i < 50000; i++) {
           variables[i] = "s"+i;
        }
        long startTime0 = System.currentTimeMillis();
        
        for(int i = 0; i < 50000; i++) {
           variables[i] = "hello";
        }
        long endTime0 = System.currentTimeMillis();
        System.out.println("Creation time" 
           + " of String literals : "+ (endTime0 - startTime0) 
           + " ms" );
        long startTime1 = System.currentTimeMillis();
        
        for(int i = 0; i < 50000; i++) {
           variables[i] = new String("hello");
        }
        long endTime1 = System.currentTimeMillis();
        System.out.println("Creation time of" 
           + " String objects with 'new' key word : " 
           + (endTime1 - startTime1)
           + " ms");
        long startTime2 = System.currentTimeMillis();
        
        for(int i = 0; i < 50000; i++) {
           variables[i] = new String("hello");
           variables[i] = variables[i].intern();       
        }
        long endTime2 = System.currentTimeMillis();
        System.out.println("Creation time of" 
           + " String objects with intern(): " 
           + (endTime2 - startTime2)
           + " ms");
     }
  }
  

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  结果

  上面的代码示例将产生以下结果。结果可能会有所不同。

  
  Creation time of String literals : 0 ms
  Creation time of String objects with 'new' key word : 31 ms
  Creation time of String objects with intern(): 16 ms