What is the name of the method that threads can use to pause their execution until signalled to continue by another thread？ （） Fill in the name of the method （do not include a parameter list）.

Which code fragments will succeed in printing the last argument given on the command line to the standard output， and exit gracefully with no output if no arguments are given？（）  
CODE FRAGMENT a：  
public static void main（String args[]） { 
 if （args.length != 0）  
System.out.println（args[args.length-1]）； 
 }  
CODE FRAGMENT b：  
public static void main（String args[]） {  
try { System.out.println（args[args.length]）； }  
catch （ArrayIndexOutOfBoundsException e） {} 
 }  
CODE FRAGMENT c：  
public static void main（String args[]） {  
int ix = args.length；  
String last = args[ix]；  
if （ix != 0） System.out.println（last）；  
}  
CODE FRAGMENT d：  
public static void main（String args[]） {  
int ix = args.length-1；  
if （ix > 0） System.out.println（args[ix]）； 
 }  
CODE FRAGMENT e：  
public static void main（String args[]） {  
try { System.out.println（args[args.length-1]）； 
}catch （NullPointerException e） {} 
 }