如何優化字符串創建？

解決方法

下麵的例子使用 String.intern()方法優化字符串創建。

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");
   }
}

結果

上麵的代碼示例將產生以下結果。該結果可能會不同。

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