SCJP : Regular Expression Mock Exam Practice Questions

Questions no -1 
What is the output for the below code ?

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {
	
	public static void main(String... args) {
            
		Pattern p = Pattern.compile("a*b");
		Matcher m = p.matcher("b");
		boolean b = m.matches();
		System.out.println(b);

		

	}
}




options
A)true
B)Compile Error
C)false
D)b

Correct answer is : A

Explanations : a*b means "a" may present zero or more time and "b" should be present once.

Questions no -2 
What is the output for the below code ?

public class Test {
	
	public static void main(String... args) {
            
		
		String input = "1 fish 2 fish red fish blue fish";
		Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");
		System.out.println(s.nextInt());
		System.out.println(s.nextInt());
		System.out.println(s.next());
		System.out.println(s.next());
		s.close(); 
		

	}
}




options
A)1 2 red blue
B)Compile Error - because Scanner is not defind in java.
C)1 fish 2 fish red fish blue fish
D)1 fish 2 fish red blue fish

Correct answer is : A

Explanations : java.util.Scanner is a simple text scanner which can parse primitive types and strings using regular expressions.

Questions no -3 
What is the output for the below code ?

public class Test {
	
	public static void main(String... args) {
            
		Pattern p = Pattern.compile("a{3}b?c*");
		Matcher m = p.matcher("aaab");
		boolean b = m.matches();
		System.out.println(b);

		

	}
}




options
A)true
B)Compile Error 
C)false
D)NullPointerException

Correct answer is : A

Explanations :
X?  X, once or not at all 
X*  X, zero or more times 
X+  X, one or more times 
X{n}  X, exactly n times 
X{n,}  X, at least n times 
X{n,m}  X, at least n but not more than m times

Questions no -4 
What is the output for the below code ?

public class Test {
	
	public static void main(String... args) {
            
		Pattern p = Pattern.compile("a{1,3}b?c*");
		Matcher m = p.matcher("aaab");
		boolean b = m.matches();
		System.out.println(b);

		

	}
}




options
A)true
B)Compile Error 
C)false
D)NullPointerException

Correct answer is : A

Explanations :
X?  X, once or not at all 
X*  X, zero or more times 
X+  X, one or more times 
X{n}  X, exactly n times 
X{n,}  X, at least n times 
X{n,m}  X, at least n but not more than m times