public String makinStrings（） { 
String s = “Fred”； 
s = s + “47”； 
s = s.substring（2， 5）； 
s = s.toUpperCase（）； 
return s.toString（）； 
} 
How many String objects will be created when this method is invoked？（） 

public class MyLogger {  private StringBuilder logger =...

单项选择题

public class MyLogger { 
private StringBuilder logger = new StringBuuilder（）； 
public void log（String message， String user） { 
logger.append（message）； 
logger.append（user）； 
} 
} 
The programmer must guarantee that a single MyLogger object works properly for a multi-threaded system. How must this code be changed to be thread-safe？（） 

Given this method in a class：  public String toString（）...

单项选择题

Given this method in a class： 
public String toString（） { 
StringBuffer buffer = new StringBuffer（）； 
buffer.append（‟<‟）； 
buffer.append（this.name）； 
buffer.append（‟>‟）； 
return buffer.toString（）； 
} 
Which is true？（） 

11. class Converter {  12. public static void main（Stri...

单项选择题

11. class Converter { 
12. public static void main（String[] args） { 
13. Integer i = args[0]； 
14. int j = 12； 
15. System.out.println（”It is “ + （j==i） + “that j==i.”）； 
16. } 
17. } 
What is the result when the programmer attempts to compile the code and run it with the command java Converter 12？（）