Chapter 3 Progress Checks

1. Why are the following declarations all invalid?

int a, b, a;

float x, int;

float w, int x;

bigNumber double;

2. Assuming the following declarations are executed in sequence, why are the second and third declarations invalid?

int a, b;

int a;

float b;

3. Name six data types for numerical values.

4. Which of the following valid assignment statements (assuming the variables are properly declared)?

X= 12;

12= x;

y + y= x;

y= x + 12;

5. Evaluate the following expressions:

3 + 2 / 5 + -2 * 4

2 * (1 + -(3 / 4) / 2) * (2 - 6 % 3)

6. What is the data type of the result of the following expressions?

(3 + 5) / 7

(3 + 5) / (float) 7

(float) ((3 + 5) / 7)

7. Which of the following expressions is equivalent to

-b (c + 34)

--------

2a

a. -b * (c + 34) / 2 * a

b. -b * (c + 34) / (2 * a)

c. -b * c + 34 / (2 * a)

8. What's wrong with the following?

int age = 10;

outputBox.show(age);

9. What's wrong with the following?

int age = 20;

outputBox.show("Your age is age");

10. Will the following code work:

age = 20;

messageBox.show("Your age is " + age);

11. Draw the state-of-memory diagram for the following code:

Account latteAcct, espressoAcct;

latteAcct= new Account();

espressoAcct= new Account();

latteAcct= espressoAcct;

12. Suppose there are the following declartions:

int i= 3, j= 4, k= 5;

float x= 34.5f, y= 12.25f;

Determine the value for each of the following expressions or explain why it is not a valid expression.

10. + 1.5) / (250.0 * (i / j))

x + 1.5 / 250.0 * i / j

-x * -y * (i + j) / k

Math.min(i, Math.min(j,k))

Math.exp(3, 2)

(int) y % x

Math.pow(3, 2)

i / 5 * y

13. Suppose we have th following declarations

int m, n, i= 3, j= 4, k= 5;

float v, w, x= 34.5f, y=12.25f;

Determine the value for each of the following expressions or explain why it is not a valid expression.

w= Math.pow(3, Math.pow(i, j));

v= x / i;

w= Math.ceil(y) % k;

n= (int) x / y * i / 2;

x= Math.sqrt(i*i - 4*j*k);

m= n + i * j;

n= k /(j * i) * x + y;

i= i + 1;

w= float(x + i);

x= x / i / y / j;

14. Suppose we have the following declarations:

int i, j;

float s, y;

double u, v;

Which of the following assignments are valid?

i= x;

x= u + y;

x= 23.4 + j * y;

v= (int) x;

y= j / i * x;

15. Write the Java expressions to computer the following:

The square root of B^2 + 4AC (A and C are distinct variables).

The square root of X + 4Y^3.

The cube root of the product of X and Y.

The area Pi*R^2 of a circle.

A sinC / sin A.

16. Determine the output of the following program without running it:

/*

Program TestOutputBox

*/

import javabook.*;

class TestOutputBox {

public static void main(String args[]) {

MainWindow mainWindow;

OutputBox outputBox;

mainWindow= new MainWindow("Program TestOutputBox");

outputBox= new OutputBox(mainWindow);

mainWindow.setVisible(true);

outputBox.setVisible(true);

outputBox.printLine("one");

outputBox.print("Two");

outputBox.skipLine(1);

outputBox.print("Three");

outputBox.printLine("Four");

outputBox.skipLine(1);

outputBox.print("Five");

outputBox.printLine("Six");

}

}

17. Determine the output of the following code:

int x, y;

x= 1;

y= 2;

messageBox.show("The output is " + x + y);

messageBox.show("The output is " + (x + y));