public class Welcome1 {
// main method begins execution of Java application
public static void main(String[] args) {
System.out.println("Welcome to Java Programming!");
} // end method main
} // end class Welcome1// Addition program that displays the sum of two numbers.
import java.util.Scanner; // program uses class Scanner
public class Addition {
// main method begins execution of Java application
public static void main(String[] args) {
// create a Scanner to obtain input from the command window
Scanner input = new Scanner(System.in);
System.out.print("Enter first integer: "); // prompt
int number1 = input.nextInt(); // read first number from user
System.out.print("Enter second integer: "); // prompt
int number2 = input.nextInt(); // read second number from user
int sum = number1 + number2; // add numbers, then store total in sum
System.out.printf("Sum is %d%n", sum); // display sum
} // end method main
} // end class Addition// Account class with a double instance variable balance and a constructor
// and deposit method that perform validation.
public class Account {
private String name; // instance variable
private double balance; // instance variable
// Account constructor that receives two parameters
public Account(String name, double balance) {
this.name = name; // assign name to instance variable name
// validate that the balance is greater than 0.0; if it's not,
// instance variable balance keeps its default initial value of 0.0
if (balance > 0.0) { // if the balance is valid
this.balance = balance; // assign it to instance variable balance
}
}
// method that deposits (adds) only a valid amount to the balance
public void deposit(double depositAmount) {
if (depositAmount > 0.0) { // if the depositAmount is valid
balance = balance + depositAmount; // add it to the balance
}
}
// method returns the account balance
public double getBalance() {
return balance;
}
// method that sets the name
public void setName(String name) {
this.name = name;
}
// method that returns the name
public String getName() {
return name;
}
}// LetterGrades class uses the switch statement to count letter grades.
import java.util.Scanner;
public class LetterGrades {
public static void main(String[] args) {
int total = 0; // sum of grades
int gradeCounter = 0; // number of grades entered
int aCount = 0; // count of A grades
int bCount = 0; // count of B grades
int cCount = 0; // count of C grades
int dCount = 0; // count of D grades
int fCount = 0; // count of F grades
Scanner input = new Scanner(System.in);
System.out.printf("%s%n%s%n %s%n %s%n",
"Enter the integer grades in the range 0-100.",
"Type the end-of-file indicator to terminate input:",
"On UNIX/Linux/macOS type <Ctrl> d then press Enter",
"On Windows type <Ctrl> z then press Enter");
// loop until user enters the end-of-file indicator
while (input.hasNext()) {
int grade = input.nextInt(); // read grade
total += grade; // add grade to total
++gradeCounter; // increment number of grades
// increment appropriate letter-grade counter
switch (grade / 10) {
case 9: // grade was between 90
case 10: // and 100, inclusive
++aCount;
break; // exits switch
case 8: // grade was between 80 and 89
++bCount;
break; // exits switch
case 7: // grade was between 70 and 79
++cCount;
break; // exits switch
case 6: // grade was between 60 and 69
++dCount;
break; // exits switch
default: // grade was less than 60
++fCount;
break; // optional; exits switch anyway
}
}
// display grade report
System.out.printf("%nGrade Report:%n");
// if user entered at least one grade...
if (gradeCounter != 0) {
// calculate average of all grades entered
double average = (double) total / gradeCounter;
// output summary of results
System.out.printf("Total of the %d grades entered is %d%n",
gradeCounter, total);
System.out.printf("Class average is %.2f%n", average);
System.out.printf("%n%s%n%s%d%n%s%d%n%s%d%n%s%d%n%s%d%n",
"Number of students who received each grade:",
"A: ", aCount, // display number of A grades
"B: ", bCount, // display number of B grades
"C: ", cCount, // display number of C grades
"D: ", dCount, // display number of D grades
"F: ", fCount); // display number of F grades
}
else { // no grades were entered, so output appropriate message
System.out.println("No grades were entered");
}
}
} // break statement exiting a for statement.
public class BreakTest {
public static void main(String[] args) {
int count; // control variable also used after loop terminates
for (count = 1; count <= 10; count++) { // loop 10 times
if (count == 5) {
break; // terminates loop if count is 5
}
System.out.printf("%d ", count);
}
System.out.printf("%nBroke out of loop at count = %d%n", count);
}
} // continue statement terminating an iteration of a for statement.
public class ContinueTest {
public static void main(String[] args) {
for (int count = 1; count <= 10; count++) { // loop 10 times
if (count == 5) {
continue; // skip remaining code in loop body if count is 5
}
System.out.printf("%d ", count);
}
System.out.printf("%nUsed continue to skip printing 5%n");
}
} // Logical operators.
public class LogicalOperators {
public static void main(String[] args) {
// create truth table for && (conditional AND) operator
System.out.printf("%s%n%s: %b%n%s: %b%n%s: %b%n%s: %b%n%n",
"Conditional AND (&&)", "false && false", (false && false),
"false && true", (false && true),
"true && false", (true && false),
"true && true", (true && true));
// create truth table for || (conditional OR) operator
System.out.printf("%s%n%s: %b%n%s: %b%n%s: %b%n%s: %b%n%n",
"Conditional OR (||)", "false || false", (false || false),
"false || true", (false || true),
"true || false", (true || false),
"true || true", (true || true));
// create truth table for & (boolean logical AND) operator
System.out.printf("%s%n%s: %b%n%s: %b%n%s: %b%n%s: %b%n%n",
"Boolean logical AND (&)", "false & false", (false & false),
"false & true", (false & true),
"true & false", (true & false),
"true & true", (true & true));
// create truth table for | (boolean logical inclusive OR) operator
System.out.printf("%s%n%s: %b%n%s: %b%n%s: %b%n%s: %b%n%n",
"Boolean logical inclusive OR (|)",
"false | false", (false | false),
"false | true", (false | true),
"true | false", (true | false),
"true | true", (true | true));
// create truth table for ^ (boolean logical exclusive OR) operator
System.out.printf("%s%n%s: %b%n%s: %b%n%s: %b%n%s: %b%n%n",
"Boolean logical exclusive OR (^)",
"false ^ false", (false ^ false),
"false ^ true", (false ^ true),
"true ^ false", (true ^ false),
"true ^ true", (true ^ true));
// create truth table for ! (logical negation) operator
System.out.printf("%s%n%s: %b%n%s: %b%n", "Logical NOT (!)",
"!false", (!false), "!true", (!true));
}
} // Scope class demonstrates field and local variable scopes.
public class Scope {
// field that is accessible to all methods of this class
private static int x = 1;
// method main creates and initializes local variable x
// and calls methods useLocalVariable and useField
public static void main(String[] args) {
int x = 5; // method's local variable x shadows field x
System.out.printf("local x in main is %d%n", x);
useLocalVariable(); // useLocalVariable has local x
useField(); // useField uses class Scope's field x
useLocalVariable(); // useLocalVariable reinitializes local x
useField(); // class Scope's field x retains its value
System.out.printf("%nlocal x in main is %d%n", x);
}
// create and initialize local variable x during each call
public static void useLocalVariable() {
int x = 25; // initialized each time useLocalVariable is called
System.out.printf(
"%nlocal x on entering method useLocalVariable is %d%n", x);
++x; // modifies this method's local variable x
System.out.printf(
"local x before exiting method useLocalVariable is %d%n", x);
}
// modify class Scope's field x during each call
public static void useField() {
System.out.printf(
"%nfield x on entering method useField is %d%n", x);
x *= 10; // modifies class Scope's field x
System.out.printf(
"field x before exiting method useField is %d%n", x);
}
} // Overloaded method declarations.
public class MethodOverload {
// test overloaded square methods
public static void main(String[] args) {
System.out.printf("Square of integer 7 is %d%n", square(7));
System.out.printf("Square of double 7.5 is %f%n", square(7.5));
}
// square method with int argument
public static int square(int intValue) {
System.out.printf("%nCalled square with int argument: %d%n",
intValue);
return intValue * intValue;
}
// square method with double argument
public static double square(double doubleValue) {
System.out.printf("%nCalled square with double argument: %f%n",
doubleValue);
return doubleValue * doubleValue;
}
} 