java.util.Scanner#nextDouble ( )源码实例Demo

public static void main(String[] args) {

		// Scanner object to get input
		Scanner keyboard = new Scanner(System.in);

		// Desired future value
		System.out.print("Future value? ");
		double futureValue = keyboard.nextDouble();

		// Annual interest rate.
		System.out.print("Annual interest rate? ");
		double annualInterestRate = keyboard.nextDouble();

		// Number of years investment to draw interest
		System.out.print("Number of years? ");
		int numberOfYears = keyboard.nextInt();

		// close scanner
		keyboard.close();

		double present = calculatePresentValue(futureValue, annualInterestRate,
				numberOfYears);

		// Display the result to user
		System.out.println("You need to invest $" + present);
	}
 

private double valueOf (String text)
{
    Scanner scanner = new Scanner(text);
    scanner.useLocale(Locale.US);

    while (scanner.hasNext()) {
        if (scanner.hasNextDouble()) {
            return scanner.nextDouble();
        } else {
            scanner.next();
        }
    }

    // Kludge!
    return Double.NaN;
}
 

public static void main(String[] args) {
	Scanner input = new Scanner(System.in);

	// Prompt the user to enter a temperature between -58F and 
	// 41F and a wind speed greater than or equal to 2.
	System.out.print("Enter the temperature in Fahrenheit " +
		"between -58ºF and 41ºF: ");
	double temperature = input.nextDouble();
	System.out.print("Enter the wind speed (>= 2) in miles per hour: ");
	double speed = input.nextDouble();

	// Compute the wind chill index
	double windChill = 35.74 + 0.6215 * temperature -
							 35.75 * Math.pow(speed, 0.16) +
							 0.4275 * temperature * Math.pow(speed, 0.16);

	// Display result
	System.out.println("The wind chill index is " + windChill);
}
 

public static void main(String[] args) {
	Scanner input = new Scanner(System.in);

	// Prompt the user to enter two points
	System.out.print("Enter x1 and y1: ");
	double x1 = input.nextDouble();
	double y1 = input.nextDouble();
	System.out.print("Enter x2 and y2: ");
	double x2 = input.nextDouble();
	double y2 = input.nextDouble();

	// Calucate the distance between the two points
	double distance = Math.pow(Math.pow(x2 - x1, 2) +
							Math.pow(y2 - y1, 2), 0.5);

	// Display result
	System.out.println("The distance between the two points is " + distance);
}
 

public static void main(String[] args) {
    /* Save input */
    Scanner scan = new Scanner(System.in);
    int size = scan.nextInt();
    double [] xs = new double[size];
    double [] ys = new double[size];
    for (int i = 0; i < size; i++) {
        xs[i] = scan.nextDouble();
    }
    for (int i = 0; i < size; i++) {
        ys[i] = scan.nextDouble();
    }
    scan.close();
    
    System.out.println(pearson(xs, ys));
}
 

public static double scanDouble() {
    Scanner in = new Scanner(System.in);
    boolean okay;
    do {
        System.out.print("Enter a number: ");
        if (in.hasNextDouble()) {
            okay = true;
        } else {
            okay = false;
            String word = in.next();
            System.err.println(word + " is not a number");
        }
    } while (!okay);
    double x = in.nextDouble();
    return x;
}
 

public static void main(String[] args) {

		double distance = 0.0; // Distance
		String medium; // To hold "air", "water", or "steel"
		
		// Create a Scanner object for keyboard input.
		Scanner keyboard = new Scanner(System.in);

		// Get the user's medium of choice.
		System.out.print("Enter one of the following: air, water, or steel: ");
		medium = keyboard.nextLine();

		// Get the distance.
        System.out.print("Enter the distance the sound wave will travel: ");
        distance = keyboard.nextDouble();
        
        // calculate 
        double distanceTravelled = getDistanceTraveledInSeconds(medium, distance);
        
        // display output
        System.out.println("It will take " + distanceTravelled + " seconds.");
		
        keyboard.close();
	}
 

public static void main(String[] args) {
	// Create a Scanner
	Scanner input = new Scanner(System.in);

	// Prompt the user to enter an amout, the 
	// annual percentage yield and the number of months 
	System.out.print("Enter the initial deposit amount: ");
	double amount = input.nextDouble();
	System.out.print("Enter annual percentage yield: ");
	double percentageYield = input.nextDouble();
	System.out.print("Enter maturity period (number of months): ");
	int months = input.nextInt();

	// Display header
	System.out.println("Month  CD Value");
	// Compute and display CD worth for the number of months
	for (int m = 1; m <= months; m++) {
		amount += amount * (percentageYield / 1200);
		System.out.printf("%-7d%.2f\n", m, amount);
	}
}
 

public static void main(String[] args) {
	Scanner input = new Scanner(System.in);

	// Prompt the user to enter a point (x, y)
	System.out.print("Enter a point with two coordinates: ");
	double x = input.nextDouble();
	double y = input.nextDouble();

	// Check whether the point is within the rectangle
	// centered at (0, 0) with width 10 and height 5
	boolean withinRectangle = (Math.pow(Math.pow(x, 2), 0.5) <= 10 / 2 ) ||
									  (Math.pow(Math.pow(y, 2), 0.5) <= 5.0 / 2);

	// Display results
	System.out.println("Point (" + x + ", " + y + ") is " +
		((withinRectangle) ? "in " : "not in ") + "the rectangle");
}
 

public static void main(String[] args) {
	// Create a Scanner object
	Scanner input = new Scanner(System.in);

	// Create constant value
	final double METERS_PER_FOOT = 0.305;

	// Prompt user to enter a number in feet
	System.out.print("Enter a value for feet: ");
	double feet = input.nextDouble();

	// Convert feet into meters
	double meters = feet * METERS_PER_FOOT;

	// Display results
	System.out.println(feet + " feet is " + meters + " meters");
}
 

public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        int m = scan.nextInt();
        int n = scan.nextInt();

        double [][] X = new double[n][m + 1];
        double [][] Y   = new double[n][1];

        for (int row = 0; row < n; row++) {
            X[row][0] = 1;
            for (int col = 1; col <= m; col++) {
                X[row][col] = scan.nextDouble();
            }
            Y[row][0] = scan.nextDouble();
        }

        /* Calculating B */
        double [][] xtx    = multiply(transpose(X),X);
        double [][] xtxInv = invert(xtx);
        double [][] xty    = multiply(transpose(X), Y);
        double [][] B      = multiply(xtxInv, xty);

        int sizeB = B.length;

        /* Calculating values for "q" feature sets */
        int q = scan.nextInt();
        for (int i = 0; i < q; i++) {
            double result = B[0][0];
            for (int row = 1; row < sizeB; row++) {
                result += scan.nextDouble() * B[row][0];
            }
            System.out.println(result);
        }

        scan.close();
    }
 

public static void main(String[] args) {
	// Create a Scanner
	Scanner input = new Scanner(System.in);

	// Tax rates
	double[] rates = {0.10, 0.15, 0.25, 0.28, 0.33, 0.35};

	// The brackets for each rate for all the filing statuses
	int[][] brackets = {
		{8350, 33950, 82250, 171550, 372950},  // Single filer
		{16700, 67900, 137050, 20885, 372950}, // Married jointly
															// -or qualifying widow(er)
		{8350, 33950, 68525, 104425, 186475},  // Married separately
		{11950, 45500, 117450, 190200, 372950} // Head of household
	};
		
	// Prompt the user to enter filing status
	System.out.print("(0-single filer, 1-married jointly or " +
		"qualifying widow(er), 2-married separately, 3-head of " +
		"household) Enter the filing status: ");
	int status = getStatus();

	// Prompt the user to enter taxable income
	System.out.print("Enter the taxable income: ");
	double income = input.nextDouble();


	// Display the result
	System.out.printf("Tax is $%6.2f\n", 
		computeTax(brackets, rates, status, income)); 
}
 

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int i = sc.nextInt();
    double d = sc.nextDouble(); 
    sc.nextLine(); 
    String s = sc.nextLine();

    System.out.println("String: " + s);
    System.out.println("Double: " + d);
    System.out.println("Int: " + i);
}
 

/** Main Method */
public static void main(String[] args) {
	Scanner input = new Scanner(System.in); // Create a Scanner

	// Prompt the user to enter the number of sides 
	// and the side of a regular polygon
	System.out.print("Enter the number of sides: ");
	int n = input.nextInt();
	System.out.print("Enter the side: ");
	double side = input.nextDouble();

	// Display the area of the regular polygon
	System.out.println("The area of the polygon is " + area(n, side));

}
 

public static double scanDouble2() {
    Scanner in = new Scanner(System.in);
    while (true) {
        System.out.print("Enter a number: ");
        if (in.hasNextDouble()) {
            break;
        }
        String word = in.next();
        System.err.println(word + " is not a number");
    }
    double x = in.nextDouble();
    return x;
}
 

public static void main(String[] args) {
	Scanner input = new Scanner(System.in);	// Create Scanner object

	// Prompt the user to enter the center x, y coorginates,
	// width, and height of two rectangles
	System.out.print("Enter r1's center x-, y-coordinates, width and height: ");
	double r1x = input.nextDouble();
	double r1y = input.nextDouble();
	double r1Width = input.nextDouble();
	double r1Height = input.nextDouble();
	System.out.print("Enter r2's center x-, y-coordinates, width and height: ");
	double r2x = input.nextDouble();
	double r2y = input.nextDouble();
	double r2Width = input.nextDouble();
	double r2Height = input.nextDouble();

	// Determine whether the second rectangle is inside the first
	if	((Math.pow(Math.pow(r2y - r1y, 2), .05) + r2Height / 2 <= r1Height / 2) && 
		(Math.pow(Math.pow(r2x - r1x, 2), .05) + r2Width / 2 <= r1Width / 2) &&
		(r1Height / 2 + r2Height / 2 <= r1Height) &&
		(r1Width / 2 + r2Width / 2 <= r1Width))
		System.out.println("r2 is inside r1");
	else if ((r1x + r1Width / 2 > r2x - r2Width) ||
				(r1y + r1Height / 2 > r2y - r2Height))
		System.out.println("r2 overlaps r1");
	else
		System.out.println("r2 does not overlap r1");
}
 

public static void main(String[] args) {
  Scanner input = new Scanner(System.in);

  System.out.print("Enter a degree in Fahrenheit: ");
  double fahrenheit = input.nextDouble(); 

  // Convert Fahrenheit to Celsius
  double celsius = (5.0 / 9) * (fahrenheit - 32);
  System.out.println("Fahrenheit " + fahrenheit + " is " + 
    celsius + " in Celsius");  
}
 

public static void main(String args[]) {

		// Create a Scanner object for keyboard input.
		Scanner keyboard = new Scanner(System.in);

		// Ask user to enter starting balance
		System.out.print("How much money is in the account?: ");
		double startingBalance = keyboard.nextDouble();

		// Ask user for annual interest rate
		System.out.print("Enter the annual interest rate:");
		double annualInterestRate = keyboard.nextDouble();

		// Create class
		SavingsAccountClass savingAccountClass = new SavingsAccountClass();
		SavingsAccount savingsAccount = savingAccountClass.new SavingsAccount(
				startingBalance, annualInterestRate);

		// Ask how long account was opened
		System.out.print("How long has the account been opened? ");
		double months = keyboard.nextInt();

		double montlyDeposit;
		double monthlyWithdrawl;
		double interestEarned = 0.0;
		double totalDeposits = 0;
		double totalWithdrawn = 0;

		// For each month as user to enter information
		for (int i = 1; i <= months; i++) {

			// Get deposits for month
			System.out.print("Enter amount deposited for month: " + i + ": ");
			montlyDeposit = keyboard.nextDouble();
			totalDeposits += montlyDeposit;

			// Add deposits savings account
			savingsAccount.deposit(montlyDeposit);

			// Get withdrawals for month
			System.out.print("Enter amount withdrawn for " + i + ": ");
			monthlyWithdrawl = keyboard.nextDouble();
			totalWithdrawn += monthlyWithdrawl;

			// Subtract the withdrawals
			savingsAccount.withdraw(monthlyWithdrawl);

			// Add the monthly interest
			savingsAccount.addInterest();

			// Accumulate the amount of interest earned.
			interestEarned += savingsAccount.getLastAmountOfInterestEarned();
		}

		// close keyboard
		keyboard.close();

		// Create a DecimalFormat object for formatting output.
		DecimalFormat dollar = new DecimalFormat("#,##0.00");

		// Display the totals and the balance.
		System.out.println("Total deposited: $" + dollar.format(totalDeposits));
		System.out
				.println("Total withdrawn: $" + dollar.format(totalWithdrawn));
		System.out
				.println("Interest earned: $" + dollar.format(interestEarned));
		System.out.println("Ending balance: $"
				+ dollar.format(savingsAccount.getAccountBalance()));
	}
 

public static void main(String[] args) throws Exception{
	Scanner reader = new Scanner(System.in);
	Integer choice = 0 ;
	do{
		Command command = null;
		choice = acceptChoice(reader);
		switch(choice){
			case 1:
				System.out.println("Enter the number");
				command = new PrimeCheckCommand(reader.nextInt());
			break;
			case 2:
				System.out.println("Enter the number");
				command = new EvenCheckCommand(reader.nextInt());
			break;
			case 3:
				System.out.println("How many primes?");
				command = new SumPrimesCommand(reader.nextInt());
			break;
			case 4:
				System.out.println("How many evens?");
				command = new SumEvensCommand(reader.nextInt());
			break;
			case 5: 
				System.out.println("How many odds?");
				command = new SumOddsCommand(reader.nextInt());
			break;
			case 6:
				System.out.println("Enter principal, rate and number of years");
				command = new SimpleInterestCommand(reader.nextDouble(), 
					reader.nextInt(), reader.nextInt());
			break;
			case 7:
				System.out.println("Enter principal, rate, number of compunds per year " + 
					"and number of years");
				command = new CompoundInterestCommand(reader.nextDouble(), 
					reader.nextInt(), reader.nextInt(), reader.nextInt());
			break;
		}
		if ( command != null ){
			command.execute();
		}
	}while(choice < 8 && choice > 0);
}
 

public static void main(String[] args) {

		System.out.println(
				"Welcome to the data points calculator! This program creates a table of values based on a given formula.");
		System.out.println();
		System.out.print("Please insert your equation in terms of x. Separate each term with a space (Ex: x^2 + 2*x + 3   You MUST include all signs (2x should be 2*x)): y = ");

		Scanner scan = new Scanner(System.in);
		String formula = scan.nextLine();
		String revisedFormula = formula;
		
		System.out.println();

		System.out.print("Left bound of your domain? ");
		double leftBound = scan.nextDouble();

		System.out.println();

		System.out.print("Right bound of your domain? ");
		double rightBound = scan.nextDouble();

		System.out.println();

		System.out.print("Step of your function (the increments at which the function is evaluated at: ");
		double step = scan.nextDouble();

		System.out.println("     x     " + "          y");
		System.out.println("_____________________________");
		
		for (double i = leftBound; i <= rightBound; i += step) {

			String input = Double.toString(i);
			revisedFormula = formula.replaceAll("x", input);
			System.out.println(input + "     |     " + eval(revisedFormula));
			
		}
		
		scan.close();

	}