formtext_formtextnum.html

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<TITLE>Creating a Text Field to Display and Edit a Number
(Java Developers Almanac Example)
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<h3>
    e752.  
    Creating a Text Field to Display and Edit a Number</h3>

This example uses a <code>JFormattedTextField</code> to allow the display and
editing of a number. By default, when the component loses the focus
and the modified value is a valid date, the modified value is
saved. Otherwise, if the modified value is not a valid date, the
modified value is discarded and the old value is displayed.


<pre>
    // Support an integer number; if a decimal point is typed,
    // the decimal point and all following characters are discarded
    JFormattedTextField tft1 = new JFormattedTextField(new Integer(<font color="#0066ff"><i>123</i></font>));
    DefaultFormatter fmt = new NumberFormatter(NumberFormat.getIntegerInstance());
    DefaultFormatterFactory fmtFactory = new DefaultFormatterFactory(fmt, fmt, fmt);
    tft1.setFormatterFactory(fmtFactory);
    
    // Retrieve the value from the text field
    Integer intValue = (Integer)tft1.getValue();
    
    
    // Support a decimal number with one digit following the decimal point;
    // if more digits after the decimal point is typed, the value is rounded to one decimal place
    JFormattedTextField tft2 = new JFormattedTextField(new Float(<font color="#0066ff"><i>123.4F</i></font>));
    fmt = new NumberFormatter(new DecimalFormat("#.0"));
    fmtFactory = new DefaultFormatterFactory(fmt, fmt, fmt);
    tft2.setFormatterFactory(fmtFactory);
    
    // Retrieve the value from the text field
    Float floatValue = (Float)tft2.getValue();
    
    
    // Support a decimal number with arbitrary number of decimal digits.
    // Actually, this isn't technically possible using DecimalFormat;
    // the best that we can do is to specify lots of #'s
    JFormattedTextField tft3 = new JFormattedTextField(new BigDecimal(<font color="#0066ff"><i>"123.4567"</i></font>));
    fmt = new NumberFormatter(new DecimalFormat("#.0###############"));
    fmt.setValueClass(tft3.getValue().getClass());
    fmtFactory = new DefaultFormatterFactory(fmt, fmt, fmt);
    tft3.setFormatterFactory(fmtFactory);
    
    // Retrieve the value from the text field
    BigDecimal bigValue = (BigDecimal)tft3.getValue();
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