Java認(rèn)證考試章節(jié)練習(xí)(2019.03.06)

Given a header in an HTTP request：X-Retries：4
Which two retrieve the value of the header from a given HttpServletRequest request？（）

現(xiàn)有：D  
- f 是一個對 java.io.File 實例的合法引用  
- fw 是一個對 java.io.FileWriter 實例的合法引用  
- bw 是一個對 java.io.BufferedWriter 實例的合法引用  
以下哪一項無效？（）  

public class foo { 
static String s； 
public static void main （String[]args） { 
system.out.printIn （“s=” + s）； 
}
} 
What is the result？（）  

10. public class ClassA { 
11. public void count（int i） { 
12. count（++i）； 
13. } 
14. } 
And： 
20. ClassA a = new ClassA（）； 
21. a.count（3）； 
Which exception or error should be thrown by the virtual machine？（） 

1. class Super { 
2. public float getNum（） { return 3.0f； } 
3. } 
4.  
5. public class Sub extends Super { 
6.  
7. } 
Which method， placed at line6， causes compilation to fail？（）  

Servlet A receives a request that it forwards to servlet B within another web application in the same webcontainer. Servlet A needs to share data with servlet B and that data must not be visible to other servlets inA’s web application.
In which object can the data that A shares with B be stored？（）