How to set result in textbox using java netbeans

I’m trying to develop program that the user will enter a text in textbox (plaintext) then the user have to select a key buttons (key_128) (key_192) (key_256) then it will click on button (encrypt_data) to encrypt the text that the user entered. Then it will show the output in another textbox (encrypt) This is the source code I’m working on

public class MARS extends javax.swing.JFrame {

static Cipher cipher;

private static int[] K;


private static final int [] s_box ={

// s_box values here };

private static int rotl(int val, int pas) {
    return (val << pas) | (val >>> (32 - pas));
}
private static int rotr(int val, int pas) {
    return (val >>> pas) | (val << (32-pas));
}


private static int[] expandKey(byte[] key){
    int n = key.length/4;
    int[] tmp = new int[40];
    int[] data = new int[n];

    for(int i =0;i<data.length;i++)
        data[i] = 0;

    int off = 0;
    for(int i=0;i<data.length;i++){
        data[i] =   ((key[off++]&0xff))|
                    ((key[off++]&0xff) << 8) |
                    ((key[off++]&0xff) << 16) |
                    ((key[off++]&0xff) << 24);
    }

    int[] T = new int[15];
    for(int i=0;i<T.length;i++){
        if(i<data.length) T[i] = data[i];
        else if(i == data.length) T[i] = n;
        else T[i] = 0;
    }

    for(int j=0;j<4;j++){
        for(int i=0;i<T.length;i++)
            T[i] = T[i] ^ (rotl(T[Math.abs(i-7 %15)] ^ T[Math.abs(i-2 %15)],3) ^ (4*i+j));
        for(int c=0;c<4;c++)
            for(int i=0;i<T.length;i++)
                T[i] = T[i] + rotl(s_box[(int)(T[Math.abs(i-1%15)] & 0x000001ff)],9);
        for(int i = 0;i<=9;i++) tmp[10*j+i] = T[4*i%15];
    }

    int[] B = {0xa4a8d57b, 0x5b5d193b, 0xc8a8309b, 0x73f9a978};
    int j,w,m,r,p;
    for(int i = 5;i<=35;i++){
        j = tmp[i] & 0x00000003;
        w = tmp[i] | 0x00000003;
        m = generateMask(w);
        r = tmp[i-1] & 0x0000001f;
        p = rotl(B[j],r);
        tmp[i] = w ^ (p & m); 
    }

    return tmp;
}

private static int generateMask(int x){
    int m;

    m = (~x ^ (x>>>1)) & 0x7fffffff;
    m &= (m >> 1) & (m >> 2); 
    m &= (m >> 3) & (m >> 6); 

    if(m == 0) 
        return 0;

    m <<= 1; m |= (m << 1); m |= (m << 2); m |= (m << 4);

    m |= (m << 1) & ~x & 0x80000000;

    return m & 0xfffffffc;

}


public static byte[] encryptBloc(byte[] in){
    byte[] tmp =  new byte[in.length];
    int aux;


    int[] data = new int[in.length/4];
    for(int i =0;i<data.length;i++)
        data[i] = 0;
    int off = 0;
    for(int i=0;i<data.length;i++){
        data[i] =   ((in[off++]&0xff))|
                    ((in[off++]&0xff) << 8) |
                    ((in[off++]&0xff) << 16) |
                    ((in[off++]&0xff) << 24);
    }

    int A = data[0],B = data[1],C = data[2],D = data[3];
    A = A + K[0];
    B = B + K[1];
    C = C + K[2];
    D = D + K[3];

    //forward mixing
    for(int i = 0;i<=7;i++){
        B = B ^ s_box[A & 0xff];
        B = B + s_box[(rotr(A,8) & 0xff) + 256]; 
        C = C + s_box[rotr(A,16) & 0xff]; 
        D = D ^ s_box[(rotr(A,24) & 0xff) + 256]; 

        A = rotr(A,24);

        if(i == 1 || i == 5) A = A + B;
        if(i == 0 || i == 4) A = A + D;

        aux = A;
        A = B;
        B = C;
        C = D;
        D = aux;
    }
    int R,L,M;
    int[] eout;
    //cryptographic core
    for(int i = 0;i<=15;i++){

        eout = E_func(A, K[2*i+4], K[2*i+5]);

        A = rotl(A,13);
        C = C + eout[1];

        if(i<8) {
            B = B + eout[0];
            D = D ^ eout[2];
        }
        else{
            D = D + eout[0];
            B = B ^ eout[2];
        }

        aux = A;
        A = B;
        B = C;
        C = D;
        D = aux;
    }
    //backward mixing
    for(int i = 0;i<=7;i++){

        if(i == 3 || i == 7) A = A - B;
        if(i == 2 || i == 6) A = A - D;

        B = B ^ s_box[(A & 0xff) + 256];
        C = C - s_box[rotr(A,24) & 0xff];
        D = D - s_box[(rotr(A,16) & 0xff) + 256];
        D = D ^ s_box[rotr(A,8) & 0xff];

        A = rotl(A,24);

        aux = A;
        A = B;
        B = C;
        C = D;
        D = aux;

    }
    A = A - K[36];
    B = B - K[37];
    C = C - K[38];
    D = D - K[39];

    data[0] = A;data[1] = B;data[2] = C;data[3] = D;

    for(int i = 0;i<tmp.length;i++){
        tmp[i] = (byte)((data[i/4] >>> (i%4)*8) & 0xff);
    }

    return tmp; 
}

private static int[] E_func(int in,int k1,int k2){
    int[] tmp = new int[3];
    int M,L,R;
    M = in + k1;
    R = rotl(in,13) * k2;
    L = s_box[M & 0x000001ff];
    R = rotl(R,5);
    M = rotl(M,R & 0x0000001f);
    L = L ^ R;
    R = rotl(R,5);
    L = L ^ R;
    L = rotl(L,R & 0x0000001f);

    tmp[0] = L;
    tmp[1] = M;
    tmp[2] = R;

    return tmp;
}

public static byte[] encrypt(byte[] in,byte[] key){
    K = expandKey(key);
    int lenght=0;
    byte[] padding = new byte[1];
    int i;
    lenght = 16 - in.length % 16;               
    padding = new byte[lenght];                 
    padding[0] = (byte) 0x80;

    for (i = 1; i < lenght; i++)                
        padding[i] = 0;

    byte[] tmp = new byte[in.length + lenght];      
    byte[] bloc = new byte[16]; 

    int count = 0;

    for (i = 0; i < in.length + lenght; i++) {
        if (i > 0 && i % 16 == 0) {
            bloc = encryptBloc(bloc);
            System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
        }
        if (i < in.length)
            bloc[i % 16] = in[i];
        else{                                                       
            bloc[i % 16] = padding[count % 16];
            count++;
        }
    }
    if(bloc.length == 16){
        bloc = encryptBloc(bloc);
        System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
    }

    return tmp;
}

This is the code I wrote in (encrypt_data) button but it gives error :(

byte[] plain = plaintext.getText().getBytes();
    if (key_128.isSelected())
   {
     byte[] K = getText().getBytes();
   }

   else if (key_192.isSelected())
   {
     byte[] K = getText().getBytes();
   }
 else if (key_256.isSelected()){
    byte[] K = getText().getBytes();
 }
   byte[] encrypted = encrypt(plain, K);
   String encrypted = encrypt.setText();

And I need to set values in key buttons (key_128) (key_192) (key_256). How I can do that in java? Each key will have binary value. The problem is in last night where showing the result in text box. And in getting text from buttons