Java IO.pdf - Nguyen Dang Binh

Java I/O
align the decimal points in a column of numbers. You create a FieldPosition object by
passing one of these numeric constants into the FieldPosition() constructor:
public FieldPosition(int field)
For example, to get the integer field:
FieldPosition fp = new FieldPosition(NumberFormat.INTEGER_FIELD);
There's a getField() method that returns this constant:
public int getField()
Next you pass this object into one of the format() methods that takes a FieldPosition
object as an argument:
NumberFormat nf = NumberFormat().getNumberInstance();
StringBuffer sb = nf.format(2.71828, new StringBuffer(), fp);
When format() returns, the FieldPosition object contains the beginning and ending index
of the field in the string. These methods return those items:
public int getBeginIndex()
public int getEndIndex()
You can subtract getBeginIndex() from getEndIndex() to find the number of characters in
the field. If you're working with a monospaced font, this may be all you need to know. If
you're working with a proportionally spaced font, you'll probably use
java.awt.FontMetrics to measure the exact width of the field instead. Example 16.6 shows
how to work in a monospaced font. This is essentially another version of the angle table. Now
a FieldPosition object is used to figure out how many spaces to add to the front of the
string; the getSpaces() method is simply used to build a string with a certain number of
spaces.
Example 16.6. PrettierTable
import java.text.*;
public class PrettierTable {
public static void main(String[] args) {
NumberFormat myFormat = NumberFormat.getNumberInstance();
FieldPosition fp = new FieldPosition(NumberFormat.INTEGER_FIELD);
myFormat.setMaximumIntegerDigits(3);
myFormat.setMaximumFractionDigits(2);
myFormat.setMinimumFractionDigits(2);
System.out.println("Degrees Radians Grads");
for (double degrees = 0.0; degrees < 360.0; degrees++) {
String radianString = myFormat.format(
radianString = getSpaces(3 - fp.getEndIndex()) + radianString;
String gradString = myFormat.format(
gradString = getSpaces(3 - fp.getEndIndex()) + gradString;
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