高效比较String常量

见java.io.FilePermission.getMask(String actions)函数

java 代码

private static int getMask(String actions){
     if (actions == SecurityConstants.FILE_READ_ACTION) {
          return READ;
     } else if (actions == SecurityConstants.FILE_WRITE_ACTION) {
          return WRITE;
     } else if (actions == SecurityConstants.FILE_EXECUTE_ACTION) {
          return EXECUTE;
     } else if (actions == SecurityConstants.FILE_DELETE_ACTION) {
          return DELETE;
     }
}

直接将字符串常量用“==”比较，显著提高了运行时效率！