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问题 填空题

在Java线程中，共享数据的所有访问都必须作为临界区，使用 【13】 进行加锁控制。

答案

参考答案：synchronized

解析： 本题考查线程同步的基本知识。临界区是指一个程序中单独的、并发的线程对一个对象进行访问的代码段。在Java线程中，共享数据的所有访问都必须作为临界区，临界区可以是一个语句块或是一个方法，并且用“synchronized”关键字标识。Java平台将每个由synchronized语句指定的对象设置一个锁，称为对象锁。Java中的对象锁是一种独占的排他锁。这种锁的含义是，当一个线程获得了对象的锁后，便拥有该对象的操作权，其他任何线程不能对该对象进行任何操作。
经过上述分析，可知划线处应填入“synchronized”。

句型转换

按要求改变下列句子。

1. I have some nice books.（否定句）

                                                                                     

2. My name is Lily.（用 what 提问） 

                                                                                    

3. This is Peter's bag.（用 whose 提问）

                                                                                     

4. This is a pencil.（一般疑问句）  

                                                                                    

5. Mike is under the big tree.（用 where 提问） 

                                                                                    

6. Four peaches are on the table.（用 how many 提问）

                                                                                      
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填空题

Questions 19-25


·Read the following article from a magazine and answer questions 19-25.
·For questions 19-25, choose the correct answer A, B, C or D.
·Mark your answer on the Answer Sheet.

The Big Easy on the Brink


A Category 5 hurricane would come barreling out of the Gulf of Mexico, It would cause Lake Pontchartrain, north of New Orleans, to overflow, pouring down millions of gallons of water on the city. Then things would really get ugly. Evacuation routes would be blocked. Buildings would collapse. Chemicals and hazardous waste would dissolve, turning the floodwaters into a lethal soup. In the end, what was left of the city might not be worth saving. "There’s concern it would essentially destroy New Orleans," says Suhayda, a water-resources expert at Louisiana State University.
New Orleans has always had a complicated relationship with the water surrounding it. Everyone told the first settlers this was the wrong place to build a city. It is wedged precariously between the mighty Mississippi and Lake Pontchartrain, and most of it was once swampland. Aggravating the problem is the fact that much of New Orleans is below sea level, so that after a good rain, the water just settles in. There is now a decent pumping system, which helps. Old-timers, however, still talk of the days when, after a bad storm, bodies were washed out of the cemeteries.
What is threatening New Orleans is a combination of two man-made problems: more levees and fewer wetlands. The levees installed along the Mississippi to protect the city from water surges have had an annoying effect: they have actually make it more vulnerable to flooding. That’s because New Orleans has been kept in place by the precarious balance of two opposing forces. Because the city is constructed on 100 feet of soft silt, sand and clay, it naturally "subsides", or sinks, several feet a century. Historically, that subsidence has been counteracted by sedimentation: new silt, sand and clay that are deposited when the river floods. But since the levees went up-mostly after the great flood of 1927—the river has not been flooding and sedimentation has stopped.
New Orleans’ other major man-made problem is that its wetlands and its low-lying barrier islands are disappearing. The Louisiana coast is losingl6,000 acres of wetland each year, mostly as a result of population expansion into once pristine areas, destructive oil and gas drilling, pollution and land loss through lack of sedimentation. As it turns out, wetland, and barrier islands aren’t just nice to look at; they are also a key natural barrier to hurricanes. (Every 2.7miles of wetland absorbs a foot of storm surge.) As the wetlands go, the chance of a hurricane blowing the city away grows.
So far, little has been done to save the city. However, while the grimmest of the doomsayers warn that New Orleans could be next Atlantis, some laid-back residents are saying that it could just as easily become the next Venice and that after the flood, the good times won’t roll—they’ll float.

New Orleans was not a good place to build a city because ______.

A．it was far away from other big cities

B．it was surrounded with giant rivers

C．it was ugly looking

D．most of it was wetland
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