Java程序辅导

Solutions to Java Lab 2 
 
1. (1 point) Create a new class called UsingControlStructures. 
 
2. (2 points) Add a main method to the class, and in the main method declare and initialize 
a variable to represent a person's age. 
 
3. (2 points) In the main method, write an if-else construct to print out "You are old 
enough to drive" if the person is old enough to drive and "You are not old enough to 
drive" if the person is too young. 
 
class UsingControlStructures { 
  public static void main(String[] args) { 
    int age = 15; 
    if (age >= 18) { 
      System.out.println("You are old enough to drive."); 
    } else { 
      System.out.println("You are not old enough to drive."); 
    } 
  } 
} 
 
4. (3 points) Write a for loop that prints out all the odd numbers from 100 to 0 in 
decreasing order. 
 
for (int i = 100; i > 0; i--) { 
  if (i % 2 == 1) { 
    System.out.println(i); 
  } 
} 
 or 
 
for (int i = 99; i > 0; i -= 2) { 
  System.out.println(i); 
} 
 
5. (2 points) Do Step 4 with a while loop instead of a for loop. 
 
int i = 100; 
while(i > 0) { 
  if (i % 2 == 1) { 
    System.out.println(i); 
  } 
  i--; 
} 
 or 
 
int i = 99; 
while(i > 0) { 
    System.out.println(i); 
    i--; 
}