Which statements concerning casting and conversion are true？（）  

Given the following code， which statements concerning t...

多项选择题

Given the following code， which statements concerning the objects referenced through the member variables i， j and k are true， given that any thread may call the methods a， b and c at any time？ （） 
class Counter {  int v = 0；  
synchronized void inc（） { v++； }  
synchronized void dec（） { v--； }  
}  
public class Q7ed5 {  
Counter i；  
Counter j；  
Counter k；  
public synchronized void a（） {  
i.inc（）；  
System.out.println（"a"）；  
i.dec（）；  }  
public synchronized void b（） {  
i.inc（）； 
j.inc（）； 
k.inc（）；  
System.out.println（"b"）； 
i.dec（）； 
j.dec（）；
k.dec（）；  }  
public void c（） {  
k.inc（）；  
System.out.println（"c"）；  
k.dec（）；  
}  
}  

What will be written to the standard output when the fo...

单项选择题

What will be written to the standard output when the following program is run？（）  
public class Q03e4 {  
public static void main（String args[]） {  
String space = " "；  
String composite = space + "hello" + space + space；  
composite.concat（"world"）；  
String trimmed = composite.trim（）；  
System.out.println（trimmed.length（））； 
 }  
}  

GiventhatfileisareferencetoaFileobjectthatrepresentsadi...

单项选择题Given that file is a reference to a File object that represents a directory， which code fragments will succeed in obtaining a list of the entries in the directory？（）