JTextFieldFilter.java

package javax.swing;

import javax.swing.text.*; 

public class JTextFieldFilter extends PlainDocument {
	protected final static long serialVersionUID = 1L;//serial version
	protected static final long versionID = 2008071800003L;	//object version

	public static final String LOWERCASE  =
		"abcdefghijklmnopqrstuvwxyz";
	public static final String UPPERCASE  =
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	public static final String ALPHA   = 
		LOWERCASE + UPPERCASE;
	public static final String NUMERIC = 
		"0123456789";
	public static final String FLOAT = 
		NUMERIC + ".";
	public static final String ALPHA_NUMERIC = 
		ALPHA + NUMERIC;

	protected String acceptedChars = null;
	protected boolean negativeAccepted = false;

	public JTextFieldFilter() {
		this(ALPHA_NUMERIC);
	}
	public JTextFieldFilter(String acceptedchars) {
		acceptedChars = acceptedchars;
	}

	public void setNegativeAccepted(boolean negativeaccepted) {
		if (acceptedChars.equals(NUMERIC) ||
				acceptedChars.equals(FLOAT) ||
				acceptedChars.equals(ALPHA_NUMERIC)){
			negativeAccepted = negativeaccepted;
			acceptedChars += "-";
		}
	}

	@Override
	public void insertString(int offset, String  string, AttributeSet attr) throws BadLocationException {
		String str = string;
		
		if (str == null) return;

		if (acceptedChars.equals(UPPERCASE))
			str = str.toUpperCase();
		else if (acceptedChars.equals(LOWERCASE))
			str = str.toLowerCase();

		for (int i=0; i < str.length(); i++) {
			if (acceptedChars.indexOf(String.valueOf(str.charAt(i))) == -1)
				return;
		}

		if (acceptedChars.equals(FLOAT) || 
				(acceptedChars.equals(FLOAT + "-") && negativeAccepted)) {
			if (str.indexOf(".") != -1) {
				if (getText(0, getLength()).indexOf(".") != -1) {
					return;
				}
			}
		}

		if (negativeAccepted && str.indexOf("-") != -1) {
			if (str.indexOf("-") != 0 || offset != 0 ) {
				return;
			}
		}

		super.insertString(offset, str, attr);
	}
	public static long getVersionID() {
		return versionID;
	}
}