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Of the two constructers one works and the other doesn't when the argument is correct

i'm new to programming. i don't understand why one of the constructers I'm using to check for the validity of the characters of a string argument in the constructer does not work. the constructer should check if the entered string contains only characters G,C,A,T, else it throws an IllegalArgumentException.
I tried using an array of characters to check for the validity of the string by using the toCharArray() method on the entered string. the constructer works for invalid strings, but not for valid strings. but another constructer i used works. please let me know why the first one doesn't.
//this is the first constructer that doesn't work for me
public class Fragment {
private String nucleotideSequence;
public Fragment(String nucleotides) throws IllegalArgumentException {
char[] validityCheck = nucleotides.toCharArray();
int validityCounter = 0;
for (char c : validityCheck) {
if(c != 'G' || c != 'C' || c != 'A' || c != 'T') {
validityCounter++;
}
}
if (validityCounter != 0) {
throw new IllegalArgumentException("Invalid characters present");
}
nucleotideSequence = nucleotides;
}
}
// this is the second constructer that works
public class Fragment {
private String nucleotideSequence;
public Fragment(String nucleotides) throws IllegalArgumentException {
boolean k = false;
for(int i = 0; i < nucleotides.length(); i++){
char lol = nucleotides.charAt(i);
if(lol=='A'||lol=='G'||lol=='C'||lol=='T'){
k = true;
}
else{
k = false;
}
if(k == false){
throw new IllegalArgumentException("Dosent work");
}
nucleotideSequence = nucleotides;
}
}
}

Your problem in the constructor that is not working is with the following 'if' statement:
if(c != 'G' || c != 'C' || c != 'A' || c != 'T')
This statement is always true. So the following:
for (char c : validityCheck) {
if(c != 'G' || c != 'C' || c != 'A' || c != 'T') {
validityCounter++;
}
}
equals:
for (char c : validityCheck) {
validityCounter++;
}
the correct statement would be
if(c != 'G' && c != 'C' && c != 'A' && c != 'T') {

java. do not accept 0 as first input in a text field

I'm using Java and this part of my code is for entering age in a text field that only accepts numbers, back spaces and delete. How can I also tell the code to avoid accepting 0 if its the first character ?
Thank you.
Here is the code:
private void tfAgeKeyTyped(java.awt.event.KeyEvent evt) {
char c = evt.getKeyChar();
if(!(Character.isDigit(c)) || (c == KeyEvent.VK_BACK_SPACE) || (c == KeyEvent.VK_DELETE)){
evt.consume();
}
}

Well you just need to check if your entered character isn't equal to 0 in your condition using c == '0' when the current input is empty:
if((this.currentInput.isEmpty() && (!Character.isDigit(c) || c == '0')) || !(Character.isDigit(c)) || (c == KeyEvent.VK_BACK_SPACE) || (c == KeyEvent.VK_DELETE)){
evt.consume();
}

private void tfAgeKeyTyped(final java.awt.event.KeyEvent evt) {
final char c = evt.getKeyChar();
// You need access to the current input to known if you are on the
// first character or not.
// Here I assume it exists as a private member variable.
final boolean isFirstChar = this.currentInput.isEmpty();
final boolean isValidEvent = (Character.isDigit(c) && !(isFirstChar && c == '0')) ||
(c == KeyEvent.VK_BACK_SPACE) ||
(c == KeyEvent.VK_DELETE);
if (isValidEvent) {
evt.consume();
}
}

Java Character Array Errors

I'm making a method for translating characters into their corresponding numbers e.g. a=1, b=2 ...
I've been recieving flak from the IDE about my declaration of the dictionary array. I've read the documentation and still have no idea how I would improve this.
Thanks for all your responses in advance! :D
EDIT: Formatting
public static int charNumTrans(char toBeTranslated){
//Variable init
int translated = 0;
char guessedVariable;
//Checking if between a and i
if(toBeTranslated == 'a' || toBeTranslated == 'b' || toBeTranslated == 'c' || toBeTranslated == 'd' || toBeTranslated == 'e'
|| toBeTranslated == 'f' || toBeTranslated == 'g' || toBeTranslated == 'h' || toBeTranslated == 'i'){ //Checking to see which array to use
char[] dictionary;
dictionary = new char {'0','.','1','a','2','b','3','c','4','d','5','e','6','f','7','g','8','h','9','i'};
//chekcing between j and s
}else if(toBeTranslated == 'j' ||toBeTranslated == 'k' ||toBeTranslated == 'l' ||toBeTranslated == 'm' ||toBeTranslated == 'n' ||
toBeTranslated == 'o' ||toBeTranslated == 'p' ||toBeTranslated == 'q' ||toBeTranslated == 'r' || toBeTranslated == 's'){//Checking to see if in between
dictionary[10] = {'0','j','1','k','2','l','3','m','4','n','5','o','6','p','7','q','8','r','9','s'};
}else{//Everything else will be in this data set.
char[] dictionary = {'0','t','1','u','2','v','3','w','4','x','5','y','6','z'};
}
guessedVariable = dictionary[1];
while(dictionary[guessedVariable] != toBeTranslated){
guessedVariable +=2;
}
// Assigns letter minus one of array. e.g. b = dictionary[5]. This will then assign dictionary[4] to translated.
translated = Character.getNumericValue(dictionary[guessedVariable-1]);
return translated;
}

First of all, you are not initializing your arrays outside of the if statements, meaning your code at the end won't be able to call the "dictionary" array. Second of all, the problem with using arrays in your scenario that you have different sized arrays. Third of all, in terms of how you are initializing the arrays, as people have pointed out, you need to create a new object that is correct for your data set e.g. new char[] {...}.
To fully solve your problem, you might want to consider something like this (I have initialized all of the arrays in the simplest way possible using the same method to avoid confusion):
public static int charNumTrans(char toBeTranslated){
//Variable init
int translated = 0;
char guessedVariable;
//Checking if between a and i
if(toBeTranslated == 'a' || toBeTranslated == 'b' || toBeTranslated == 'c' || toBeTranslated == 'd' || toBeTranslated == 'e'
|| toBeTranslated == 'f' || toBeTranslated == 'g' || toBeTranslated == 'h' || toBeTranslated == 'i'){ //Checking to see which array to use
char[] dictionary = {'0','.','1','a','2','b','3','c','4','d','5','e','6','f','7','g','8','h','9','i'};
return findValue(dictionary);
//checking between j and s
}else if(toBeTranslated == 'j' ||toBeTranslated == 'k' ||toBeTranslated == 'l' ||toBeTranslated == 'm' ||toBeTranslated == 'n' ||
toBeTranslated == 'o' ||toBeTranslated == 'p' ||toBeTranslated == 'q' ||toBeTranslated == 'r' || toBeTranslated == 's'){//Checking to see if in between
char[] dictionary = {'0','j','1','k','2','l','3','m','4','n','5','o','6','p','7','q','8','r','9','s'};
return findValue(dictionary);
}else{//Everything else will be in this data set.
char[] dictionary = {'0','t','1','u','2','v','3','w','4','x','5','y','6','z'};
return findValue(dictionary);
}
}
public static int findValue(char[] dictionary){
guessedVariable = dictionary[1];
while(dictionary[guessedVariable] != toBeTranslated){
guessedVariable +=2;
}
// Assigns letter minus one of array. e.g. b = dictionary[5]. This will then assign dictionary[4] to translated.
translated = Character.getNumericValue(dictionary[guessedVariable-1]);
return translated;
}

Change
dictionary = new char {'0','.','1','a','2','b','3','c','4','d','5','e','6','f','7','g','8','h','9','i'};
to
dictionary = new char[] {'0','.','1','a','2','b','3','c','4','d','5','e','6','f','7','g','8','h','9','i'};

For your array declaration, you are missing the [] when you assign the values to the array object you're creating - so, for example, change your declarations to this:
char[] dictionary = new char[]{'0','t','1','u','2','v','3','w','4','x','5','y','6','z'};
Also, if you are trying to convert letters to numerical equivalents, may I suggest that you cast the char that you've passed to the function into an int, and then subtract 61 from this value?
Reason being is that 61 corresponds to the position of the character 'a' on the Unicode character table, and would greatly simplify assigning a number to the letter that you pass in.

The if statement is redundant in Java

I am getting a lightbulb on NetBeans saying "The if statement is redundant"
I want to know how these two are equal to one another
public boolean isVowel(char in)
{
char temp = Character.toLowerCase(in);
if (temp == 'a' || temp == 'e' || temp == 'i' || temp == 'o' || temp == 'u')
{
return true;
}
else
{
return false;
}
}
and
public boolean isVowel(char in)
{
char temp = Character.toLowerCase(in);
return temp == 'a' || temp == 'e' || temp == 'i' || temp == 'o' || temp == 'u';
}
I can see how it would return true if one of the vowels matches with temp. However, I am not seeing how it would return false. Would it simply just return false if none of the conditions are met?
Solved: I was looking at the problem the wrong way. For it to return false, each conditional statement would have to be false. Ideally it would return false if the return statement was equivalent to:
return false || false || false || false || false;
and true if any one condition is met
return false || false || false || false || true;
Thanks you guys, it really helped.

The two statements are identical.
int x = #; //user input
if (x==1) { //any condition resulting in a true or false
return true;
} else {
return false;
}
and
return (x==1); //same thing, returning true if true, false if false;

This expression:
(temp == 'a' || temp == 'e' || temp == 'i' || temp == 'o' || temp == 'u')
calculates a boolean value. An if-statement tests this value. So instead of testing this expression in the ireturning the boolean value in the if/else-clause you can just return it.
Edit you can just prove if your char is a vowel?
Do it this way:
public boolean isVowel(char in) {
return "aeiou".indexOf(Character.toLowerCase(in)) < 0;
}

The two are indeed identical (and the if statement is redundant) and here's why.
The == is an equality operator, which means that, if the left side matches the right side, it evaluates to true, otherwise it evaluates to false. The || is a conditional operator, meaning that, if the equality on the left hand side evaluates to false, it will check the right side to see if it evaluates to true (or, if left side evaluates to true, then the expression will evaluate to true, called short-circuiting). If all of them evaluate to false, then the entire expression will evaluate to false.
Therefore, the if statement as you have it essentially turns into:
if(<expression>==true) { //in the case that the conditional evaluates to true
return true;
}
else { //in the case the conditional evaluates to false
return false;
}
So, that can just be reduced down to expression, since it will evaluate to a boolean anyways.
return <expression> //will be true if true, false if false
There's more on this in the Oracle documentation

boolean isNumeric(char cc){
//begin // test if cc is numeric
return (
(cc == '0')
| (cc == '1')
| (cc == '2')
| (cc == '3')
| (cc == '4')
| (cc == '5')
| (cc == '6')
| (cc == '7')
| (cc == '8')
| (cc == '9') );
} // isNumeric

How to Check Every Letter as a String

I'm failing the following test case:
#Test (timeout=3000) public void gatenot_0(){
GateNot g = new GateNot (new Wire("inw"), new Wire("outa"));
g.feed("0");
boolean ans = g.propagate();
assertEquals(sigs1, g.read());
}
which says "Invalid character" - Exception thrown by the following method:
public static List <Signal> fromString(String inps)
{
List<Signal> values = new ArrayList<Signal>();
for(int i = 0; i < inps.length(); i++)
{
if(inps.charAt(i) != '1' && inps.charAt(i) != '0'
&& inps.charAt(i) != 'X' && inps.charAt(i) != 'x'
&& inps.charAt(i) != ' ' && inps.charAt(i) != '\t')
throw new ExceptionLogicMalformedSignal(inps.charAt(0), "Invalid character!");
else if(inps.charAt(i) == '1')
values.add(HI);
else if(inps.charAt(i) == '0')
values.add(LO);
else if(inps.charAt(i) == 'X')
values.add(X);
else if(inps.charAt(i) == 'x')
values.add(X);
}
return values;
}
Everytime I pass something including "0" or "1" it throws Exception So, should I check every letter of String inps as a String instead of charAt(). If yes, how should I check that? Thanks in advance.

To check every letter as a string you could use
Character.toString(inps.charAt(i))
instead of just inps.charAt(i)
I would recommend storing it in a variable for each iteration instead of calling many times.
You could also do
String.valueOf(inps.charAt(i))
There is a shortcut
inps.charAt(i) + ""
And yet another way:
inps.substring(i, i + 1)
Note that if you end of converting each letter to string, you should use the .equals method when comparing them.
For more information about this, you can look at How to convert a char to a String?