textArea.append("nuevo texto);

textArea.setCaretPosition( textArea.getText().length() ); 

import java.io.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;


public class claseconjun {
	static ArrayList listA = new ArrayList();
	static ArrayList listB = new ArrayList();
	static ArrayList listC = new ArrayList();
	
	static void union() {
		
		listA.trimToSize();
		listB.trimToSize();
		
		for( int i = 0; i < listA.size(); i++ )
			if( listB.contains(listA.get(i)) && !listC.contains(listA.get(i)) )
				listC.add(listA.get(i));
		
		System.out.println("La union de A y B es:");
		
		Iterator it = listC.iterator();
		while( it.hasNext() )
			System.out.print(it.next() + " ");
	}

	static void interseccion() {
		listA.addAll(listB);
		Collections.sort(listA);
		
		System.out.println("La interseccion de A y B es:");
		
		Iterator it = listA.iterator();
		while( it.hasNext() )
			System.out.print(it.next() + " ");
	}

	public static void main(String[] args) throws IOException {

		System.out.println("Ingrese la Opcion ");
		System.out.println("1. Calculo  Union ");
		System.out.println("2. Calculo Interseccion");

		System.out.println("Ingrese la Opción = ");
		BufferedReader dato1 = new BufferedReader(new InputStreamReader(
				System.in));
		int OP = Integer.parseInt(dato1.readLine().trim());
		
		for (int i = 0; i < 5; i++) {
			System.out.println("Ingrese Valor en A[" + i + "] = ");
			dato1 = new BufferedReader(new InputStreamReader(System.in));
			Integer X = new Integer(Integer.parseInt(dato1.readLine().trim()));
			listA.add(i, X);
		}
		for (int i = 0; i < 5; i++) {
			System.out.println("Ingrese Valor en B[" + i + "] = ");
			BufferedReader dato2 = new BufferedReader(
					new InputStreamReader(System.in));
			Integer Y = new Integer(Integer.parseInt(dato2.readLine().trim()));
			listB.add(i, Y);
		}
		
		switch (OP) {
			case 1: 
				union();
			break;
			case 2:
				interseccion();
			break;
			default:
			System.out.println("Valor no Valido");
			break;
		}
	}
}

$result = mysql_query("SHOW COLUMNS FROM tabla");
 while ($row = mysql_fetch_assoc($result)) {
         echo $row['Field'];
     }