Membuat Program Konversi Angka dengan Java

[java]public static int pangkat (int a, int b){
int hasil=1;
for(int i=1;i<=b;i++){
hasil=hasil*a;
}
return hasil;
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                      
// TODO add your handling code here:
String bin = "";
String bilbiner = "";
int nilaiawal = 0;
int nilaisisa;
int hasilbagi = 0;
String hasil;
        nilaiawal = Integer.parseInt(txtnilai.getText());
if (jComboBox1.getSelectedIndex()== 0){
hasilbagi = nilaiawal/2;
            while(hasilbagi>=1){
nilaisisa = nilaiawal % 2;
if (nilaisisa == 0){
bin="0";
}else{
bin ="1";
}bilbiner = bin + bilbiner;
nilaiawal = hasilbagi;
hasilbagi = nilaiawal/2;
}
if (nilaiawal>0){
hasil = "1"+bilbiner;
}else {
hasil = "0";
}
txthasil.setText(String.valueOf(hasil));
        }else if (jComboBox1.getSelectedIndex()==1){
String biner = txthasil.getText();
int n, sum;
int hasilbiner;
char b[]= new char [1000];
n=biner.length();
sum=0;
            for (int i=1;i<=n;i++){
b[i]=biner.charAt(i-1);
}
for (int i=n-1;i>=0;i–){
if(b[n-i]==’0′){
sum=sum+0*pangkat(2,i);
}else if(b[n-1]==’1′){
sum=sum+1*pangkat(2,i);
}
}
hasilbiner=sum;
txthasil.setText(String.valueOf(hasilbiner));
}
}         [/java]