Java中两个判断字符串是否为空的方法的执行效率比较，java执行效率,public class

Java中两个判断字符串是否为空的方法的执行效率比较，java执行效率,public class

public class Test4  {      public static void main(String[] args)      {          long times = 999999999;          String str = "";          long a1 = System.currentTimeMillis();          for (long i = 0; i < times && str.isEmpty(); i++)          {              // System.out.println(str.isEmpty());          }          long a2 = System.currentTimeMillis();          System.out.println("str.isEmpty() times: " + (a2 - a1));          long b1 = System.currentTimeMillis();          for (long i = 0; i < times && "".equals(str); i++)          {              // System.out.println("".equals(str));          }          long b2 = System.currentTimeMillis();          System.out.println("\"\".equals(str) times: " + (b2 - b1));      }  }  

                                输出结果如下：

str.isEmpty() times: 2735  "".equals(str) times: 10516  

                                其实看下源码很快就发现问题所在                                isEmpty()函数的源码

public boolean isEmpty() {      return count == 0;      }  

                                equals的源码

public boolean equals(Object anObject) {      if (this == anObject) {          return true;      }      if (anObject instanceof String) {          String anotherString = (String)anObject;          int n = count;          if (n == anotherString.count) {          char v1[] = value;          char v2[] = anotherString.value;          int i = offset;          int j = anotherString.offset;          while (n-- != 0) {              if (v1[i++] != v2[j++])              return false;          }          return true;          }      }      return false;      }