Ctrl+K

Random Revie Problems

Random Revie Problems#

Question 1 Which import statement must be placed at the beginning of our program to use Random?

  1. import java.util;

  2. import java.util.*;

  3. import java.io;

  4. import java.io.*;

See Answer

import java.util.* is needed for our programs to use Random.

Question 2 Write a line of code that will properly construct a Random:

See Answer

Any of the following options are valid! Remember that the name of the Random variable is up to you, but all other parts of the construction code should match:

Random rand = new Random(); 

Random r = new Random(); 

Random random = new Random(); 

Random randy = new Random();

Question 3 Which line will give back a random value in the range of 0 (inclusive) to 5 (exclusive)?

  1. int num = rand.nextInt(4);

  2. int num = rand.nextInt(5);

  3. int num = rand.nextInt(6);

See Answer

Option 2 is correct!

Remember that calls to nextInt(int max) will give you a random value in the range of 0 and max - 1 (max-exclusive).

Question 4 Which line will give back a random value in the range of 1 (inclusive) to 6 (inclusive)?

  1. int num = rand.nextInt(4) + 1;

  2. int num = rand.nextInt(5) + 1;

  3. int num = rand.nextInt(6) + 1;

See Answer

Option 3 is correct!

Remember that calls to nextInt(int max) will give you a random value in the range of 0 and max - 1 (max-exclusive). So in this case, a call to rand.nextInt(6) would give back a random value from the range of 0 (inclusive) to 5 (inclusive).

By adding 1, we are shifting that range from between 0 and 5, to between 1 and 6.

Question 5 Which line will give back a random value in the range of 5 (inclusive) to 15 (inclusive)?

Hint

nextInt(range) + min, where range = max - min + 1

  1. int num = rand.nextInt(11) + 5;

  2. int num = rand.nextInt(15) + 5;

  3. int num = rand.nextInt(10) + 5;

See Answer

Option 1 is correct!

Remember that calls to nextInt(int max) will give you a random value in the range of 0 and max - 1 (max-exclusive). So in this case, a call to rand.nextInt(11) would give back a random value from the range of 0 (inclusive) to 10 (inclusive).

By adding 5, we are shifting that range from between 0 and 10, to between 5 and 15.