CS计算机代考程序代写 Java Practice Test – Fill in the blanks with Code

Practice Test – Fill in the blanks with Code
1. The following Java code that uses a for statement to sum the numbers from 1 through 50 and display the total sum to the console.
Answer:
int sum = 0;
//Two lines of code are missing here
System.out.println(“The total is: ” + sum); Ans: for(int i=1; i <= 50; i++) sum += i; 1. Write code in the blank which would produce the required output. public void drawTriangle() { int row // the row position int column ; // the column position ____________________________________ //enter code here { for ( column = 1; column <= row; column++ ) System.out.print( "*" ); System.out.println(); } // end for loop System.out.println(); } Output: ********** ********* ******** ******* ****** ***** **** *** ** * Ans: 38 for ( row = 10; row >= 1; row– )
1

2. Write code in the blank which would produce the required output.
public void drawTriangle()
{
int row; // the row position
int column; // the column position
int space; // number of spaces to print
for ( row = 10; row >= 1; row– )
{
for ( space = 10; space > row; space– )
System.out.print( ” ” );
//Fill code here
System.out.print( “*” );
System.out.println();
} // end for loop
System.out.println();
}
Output:
**********
********* ******** ******* ****** ***** **** *** **
Answer 2: for ( column = 1; column <= row; column++ ) 2 3. Identify and correct the error in the following piece of code. while ( x <= 100 ) total += x; ++x; ANS: The two statements should be enclosed in curly braces to properly group them into the body of the while; otherwise the loop will be an infinite loop. 4. The output produced by the following program is shown as it would appear on the console. Fill in the 2 lines of code that would produce the required output. public class Mystery { public static void main(String[] args) { String i = "CS"; String j = "teacher"; String k = "tough"; String teacher = "face"; String course = "tasty"; compute(k, i, j); compute(i, j, k); // Fill in the two lines of code here. compute(j, "k", j); } public static void compute(String k, String i, String j) { System.out.println("The " + j + " of " + k + " is " + i); } } Answer: compute(teacher, j, course); compute("course", k, "marty"); The teacher of tough is CS The tough of CS is teacher The tasty of face is teacher The marty of course is tough The teacher of teacher is k 3 4 6. Write ONE Java statement that computes and displays a random number between 1 and 25. Answer: System.out.println("Random number between 1 and 25 " + Math.round((Math.random() * 25))); 7. Declare and create a multidimensional array to hold the first and last names of 10 people. Answer: String[][] Names = new String[10][2]; 8. Write 3 lines of code to initialize the following 2-d array to -1.0. Double[][] myDoubles = new Double[10][10]; Answer: for(int row = 0; row < myDoubles.length; row++) for(int column = 0; column < myDoubles[row].length; column++) myDoubles[row][column] = -1.0; 9. Write a decision statement to determine if an object should be downcast and then downcast it. Answer: if(someObject instance of MyObject) MyObject m = (MyObject) someObject; 10. Define the signature for an abstract method which returns a String and takes in 3 parameters – a Double object, an integer primitive and a variable argument list of type objects. Answer: abstract String format(Double d, int s, Object... arguments);