179. Auto boxing int to Double?

• Working with Numbers
  • ➟ Number Parsing

180. Why using String userInput = null?

181. Parsing short values
182. Parsing short values in hexadecimal representation

• Working with Numbers
  • ➟ Number Formatting

A Locale object represents a specific geographical, political, or cultural region.

An operation that requires a Locale to perform its task is called locale-sensitive and uses the Locale to tailor information for the user.

For example, displaying a number is a locale-sensitive operation: Numbers should be formatted according to the customs and conventions of the user's native country, region, or culture.

final DecimalFormatSymbols unusualSymbols =
  new DecimalFormatSymbols(Locale.getDefault());
unusualSymbols.setDecimalSeparator('|');
unusualSymbols.setGroupingSeparator('^');

final String strange = "#,##0.###";
final DecimalFormat weirdFormatter = new DecimalFormat(strange, unusualSymbols);
weirdFormatter.setGroupingSize(4);

System.out.println(weirdFormatter.format(12345.678));

1^2345|678

183. Locale definitions
184. Formatting int, double and LocaleDate

final NumberFormat de = NumberFormat.getInstance(Locale.GERMANY),
                       us = NumberFormat.getInstance(Locale.US);
try {
  final Number[] values = {
    de.parse("103.234"), de.parse("400.000,234"),
    us.parse("103.234"), us.parse("400.000,234"),};
  for (final Number n: values) {
    System.out.println(n + "(" + n.getClass().getTypeName() + ")");
  } catch (ParseException e) { ... }

103234(java.lang.Long)
400000.234(java.lang.Double)
103.234(java.lang.Double)
400(java.lang.Long)

• Working with Numbers
  • ➟ Working with Money

final float result = 0.99f - 0.1f -0.1f -0.1f;
System.out.println(result);

0.68999994

final double result = 0.99 - 0.1 -0.1 -0.1;
System.out.println(result);

0.6900000000000001

final BigDecimal zero_dot_99 = new BigDecimal("0.99");
final BigDecimal zero_dot_1 = new BigDecimal("0.1");

BigDecimal 
  result = zero_dot_99.subtract(zero_dot_1);  // Subtracting 0.1

  result = result.subtract(zero_dot_1);       // Subtracting 0.1
  result = result.subtract(zero_dot_1);       // Subtracting 0.1

System.out.println(result);

0.69

final BigDecimal zero_dot_99 = new BigDecimal("0.99");
final BigDecimal zero_dot_1 = new BigDecimal("0.1");

BigDecimal result = zero_dot_99.
  subtract(zero_dot_1).
  subtract(zero_dot_1).
  subtract(zero_dot_1);

System.out.println(result);

0.69

185. Chaining subtract method calls

• Working with Numbers
  • ➟ Generating Random Numbers

for (int i = 0; i < 10; i++) {
  System.out.println(Math.random());
}

0.4754286988826202
0.0060114391743414375
...
0.9047785351372987
0.2516070321935864

try(final Scanner scanner = new Scanner(System.in)) {
  System.out.print("Enter an integer seed:");
  final long seed = scanner.nextLong();

  Random generator = new Random(seed);
  for (int i = 0; i < 10; i++) {
    System.out.print(generator.nextBoolean() + " ");
  }
}

Enter an integer seed:4237549835735
false true true true false false false true false true