Java ช่วยแนะนำวิธีแสดงข้อมูลที่ซ้ำ ให้แสดงแค่ ตัวเดียว ไม่แสดงข้อมูลตัวที่ซ้ำออกมาเรื่อยๆครับ

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

	public class Main  {
		public static String[] A = new String[150000];
		public static String[] B = new String[150000];
		public static String[] C = new String[150000];
		public static String[] D = new String[150000];
		public static String[] E = new String[150000];
		public static String[] F = new String[150000];
		public static String[] G = new String[150000];
		public static String[] H = new String[150000];
		public static String[] I = new String[150000];
		public static String[] J = new String[150000];
		public static String[] K = new String[150000];
		public static String[] L = new String[150000];
		public static String[] M = new String[150000];
		public static String[] N = new String[150000];
		public static String[] O = new String[150000];
		public static String[] P = new String[150000];
		public static String[] Q = new String[150000];
		public static String[] R = new String[150000];
		public static String[] S = new String[150000];
		public static String[] T = new String[150000];
		public static String[] U = new String[150000];
		public static String[] V = new String[150000];
		public static String[] W = new String[150000];
		public static String[] X = new String[150000];
		public static String[] Y = new String[150000];
		public static String[] Z = new String[150000];
		public static int ca = 0;
		public static int  cb = 0;
		public static int  cc = 0;
		public static int  cd = 0;
		public static int  ce = 0;
		public static int  cf = 0;
		public static int  cg = 0;
		public static int  ch = 0;
		public static int  ci = 0;
		public static int  cj = 0;
		public static int  ck = 0;
		public static int  cl = 0;
		public static int  cm = 0;
		public static int  cn = 0;
		public static int  co = 0;
		public static int  cp = 0;
		public static int  cq = 0;
		public static int  cr = 0;
		public static int  cs = 0;
		public static int  ct = 0;
		public static int  cu = 0;
		public static int  cv = 0;
		public static int  cw = 0;
		public static int  cx = 0;
		public static int  cy = 0;
		public static int  cz = 0;



		public static void insert(String key){
			
			if (key.length() > 1) {
				
			String checkback = key.substring(key.length()-1,key.length());	
			
			switch (checkback) {
			case ",":
				key = key.substring(0,key.length()-1);
				break;
			case "?":
				key = key.substring(0,key.length()-1);
				break;
			case ")":
				key = key.substring(0,key.length()-1);
				break;
			case "(":
				key = key.substring(0,key.length()-1);
				break;
			case ".":
				key = key.substring(0,key.length()-1);
				break;
			case ":":
				key = key.substring(0,key.length()-1);
				break;
			case "/":
				key = key.substring(0,key.length()-1);
				break;
			case "'":
				key = key.substring(0,key.length()-1);
				break;
			case ";":
				key = key.substring(0,key.length()-1);
				break;
			}
			
				
			
			
			String keyc = key.substring(0,1);
			
			switch (keyc) {
			case "A":
				A[ca] = key;
				ca++;
				break;
			case "a":
				A[ca] = key;
				ca++;
				break;
			case "B":
				B[cb] = key;
				cb++;
				break;
			case "b":
				B[cb] = key;
				cb++;
				break;
			case "C":
				C[cc] = key;
				cc++;
				break;
			case "c":
				C[cc] = key;
				cc++;
				break;
			case "D":
				D[cd] = key;
				cd++;
				break;
			case "d":
				D[cd] = key;
				cd++;
				break;
			case "E":
				E[ce] = key;
				ce++;
				break;
			case "e":
				E[ce] = key;
				ce++;
				break;
			case "F":
				F[cf] = key;
				cf++;
				break;
			case "f":
				F[cf] = key;
				cf++;
				break;
			case "G":
				G[cg] = key;
				cg++;
				break;
			case "g":
				G[cg] = key;
				cg++;
				break;
			case "H":
				H[ch] = key;
				ch++;
				break;
			case "h":
				H[ch] = key;
				ch++;
				break;
			case "I":
				I[ci] = key;
				ci++;
				break;
			case "i":
				I[ci] = key;
				ci++;
				break;
			case "J":
				J[cj] = key;
				cj++;
				break;
			case "j":
				J[cj] = key;
				cj++;
				break;
			case "K":
				K[ck] = key;
				ck++;
				break;
			case "k":
				K[ck] = key;
				ck++;
				break;
			case "L":
				L[cl] = key;
				cl++;
				break;
			case "l":
				L[cl] = key;
				cl++;
				break;
			case "M":
				M[cm] = key;
				cm++;
				break;
			case "m":
				M[cm] = key;
				cm++;
				break;
			case "N":
				N[cn] = key;
				cn++;
				break;
			case "n":
				N[cn] = key;
				cn++;
				break;
			case "O":
				O[co] = key;
				co++;
				break;
			case "o":
				O[co] = key;
				co++;
				break;
			case "P":
				P[cp] = key;
				cp++;
				break;
			case "p":
				P[cp] = key;
				cp++;
				break;
			case "Q":
				Q[cq] = key;
				cq++;
				break;
			case "q":
				Q[cq] = key;
				cq++;
				break;
			case "R":
				R[cr] = key;
				cr++;
				break;
			case "r":
				R[cr] = key;
				cr++;
				break;
			case "S":
				S[cs] = key;
				cs++;
				break;
			case "s":
				S[cs] = key;
				cs++;
				break;
			case "T":
				T[ct] = key;
				ct++;
				break;
			case "t":
				T[ct] = key;
				ct++;
				break;
			case "U":
				U[cu] = key;
				cu++;
				break;
			case "u":
				U[cu] = key;
				cu++;
				break;
			case "V":
				V[cv] = key;
				cv++;
				break;
			case "v":
				V[cv] = key;
				cv++;
				break;
			case "W":
				W[cw] = key;
				cw++;
				break;
			case "w":
				W[cw] = key;
				cw++;
				break;
			case "X":
				X[cx] = key;
				cx++;
				break;
			case "x":
				X[cx] = key;
				cx++;
				break;
			case "Y":
				Y[cy] = key;
				cy++;
				break;
			case "y":
				Y[cy] = key;
				cy++;
				break;
			case "Z":
				Z[cz] = key;
				cz++;
				break;
			case "z":
				Z[cz] = key;
				cz++;
				break;
				
			}
			
			}
		}


  public static void main(String[] args) {
    // A string array with duplicate values
    String[] data = { "A", "C", "B", "D", "A", "B", "E", "D", "B", "C" };
    System.out.println("Original array         : " + Arrays.toString(data));
      
			try {
				FileReader fr = new FileReader("C:\\test.txt");
				BufferedReader br = new BufferedReader(fr);
				String[] a = {};
				String line = br.readLine();
				while (line != null) {
					a = line.split(" ");
					for (int i = 0; i < a.length; i++) {
						// System.out.println(a[i]);
						if (a[i] != null) {
							insert(a[i]);
							List<String> list = Arrays.asList(data);
						    Set<String> set = new HashSet<String>(list);
						}
					}
					line = br.readLine();
				}
			} catch (IOException e) {
				System.out.println("ERROR");
			}
	

    }
  }