Develop Reference

Java && operators

I'm trying to make simple if statement , I need to see if my two String's values are not empty (does not equal "").
I use && operator , but sadly , it only checks one string properly if it's not empty , and if the second string is empty, he passes . Making && kinda useless for me.
if ( StringUtils.isNullOrEmpty(name) && StringUtils.isNullOrEmpty(sname)
) {do something}
I need them both to be checked properly . If at least one string is empty return false .
If both are not empty return true.

Currently your condition is true if both Strings are null or empty.
If you want both not to be null or empty you need :
if ( !StringUtils.isNullOrEmpty(name) && !StringUtils.isNullOrEmpty(sname)
) {do something}

&& is smart and if first condition is false it doesn't try the second.
use & could achieve what you want.

The problem is that your check is wrong. You want it to only pass if both ARE empty.
So you should go for
if ( !StringUtils.isNullOrEmpty(name) && !StringUtils.isNullOrEmpty(sname)
) {do something}
or if u want to catch it in the if statement if one of them IS empty, you should use or:
if ( StringUtils.isNullOrEmpty(name)|| StringUtils.isNullOrEmpty(sname)
) {do something}

isNullOrEmpty will return true if name is empty, but you want it NOT empty, so negate the conditions using !.
if ( !StringUtils.isNullOrEmpty(name) && !StringUtils.isNullOrEmpty(sname)
) {do something}
Another alternative is:
if (!(StringUtils.isNullOrEmpty(name) || StringUtils.isNullOrEmpty(sname)
)) {do something}
However, the above is not a recommended coding style, as it is difficult to catch the ! hidden just before the line, and code readers may get confused.
About || and && operators optimized checking:
|| checks for the first true condition from left to right and skips any further checking if it finds one true condition.
&& checks for the first false condition from left to right and skips any further checking if it finds one false condition.

At first it didn't looked any sense to me , and it didn't worked . Only then I realized that I need to to flip the return statements.
if (!StringUtils.isNullOrEmpty(name) && !StringUtils.isNullOrEmpty(sname)) {
System.out.println("ok");
return true;}
else {
System.out.println("empty names");
return false;
}
Now it seems to work just fine.

Using '&' as logical operator you can do the following thing. Here we have not use StringUtils -
if( ( null!=name && !name.isEmpty() ) &
( null!=sname && !sname.isEmpty() ) ){do something}

Finding if a specific character exists at a specific index

so I'm trying to figure out how to create a condition for my decision structure. I'm making a program that converts military time to conventional time. When times are entered, they must be in a XX:XX format, where X equals a digit. I'm wondering, how can I make a validation that checks to make sure that ":" always exists as a colon and is in the same spot?

myString.charAt(5) == ':'
Just change 5 to whatever you need, and check string length before you do this, so you don't ask for something past the end of a short string.

You could search the string with indexOf(), which returns the index at which the character is found. This will check if a colon is in the string and if it's in the right position.
if("10:00".indexOf(':') == 2)
// do something
It will return -1 if the value is not found. Check out the java documentation for more information.

Here is the answer for it
Suppose you had string that contains XX:XX
yourString="XX:XX"
yourString.contains(":") - return true - if exists
":" takes the 3rd position. So it will be 2(0,1,2)
yourString.charAt(2) == ':'
Together , it will be
if(yourString.contains(":") && yourString.charAt(2) == ':'){
//your logic here
}else{
something here
}

Here is one approach to that,
String[] test = new String[] { "00:00", "NN:NN", "12,13", "12:13" };
for (String fmt : test) {
boolean isValid = true;
for (int i = 0; i < fmt.length(); i++) {
char c = fmt.charAt(i);
if (i == 2) {
if (c != ':') { // here is the colon check.
isValid = false;
break;
}
} else {
// This checks for digits!
if (!Character.isDigit(c)) {
isValid = false;
break;
}
}
}
System.out.println(fmt + " is " + isValid);
}
Output is
00:00 is true
NN:NN is false
12,13 is false
12:13 is true

#WillBro posted a good answer but I give you another option:
myString.indexOf(":") == 5
With indexOf you can also look for full String inside a String.
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html
But for string format validations I suggest you to use Regular Expresions.
Here's a full example that does what you want to do:
http://www.mkyong.com/regular-expressions/how-to-validate-time-in-24-hours-format-with-regular-expression/

How do I link a user input argument with a string?

So, I'm rather new to Java and I just starting a project, but I ran into some issues.
My question is... How do I link a user input (argument) with a String?
I have already defined a few Strings earlier on in my code, but in this line I want it to match up and check from the String which matches the argument and check if it contains something:
if (!cs.hasPermission("foo." + args[0]) && [CODE HERE] ){
I want [CODE HERE] to check If args[0] (user input) matches a String, if it does then check if it matches some text.

Java has a .equals() method which can be used to compare two Strings. It can used to compare two variables which hold references to String objects or to compare String literals
if( args[0].equals(someString) ) { // compare args[0] to another String variable
}
if( "someText".equals(args[0]) ) { // compare args[0] to a String literal
}
Reading through the String documentation will also be very useful to you starting out.

This is String equals api, so it should look something like:
if (!cs.hasPermission("foo." + args[0]) && args[0].equals(string){
//code
}

You can easily do it with the equals() method. But you should also check that args[0] is set.
if (args.length > 0) {
if (!cs.hasPermission("foo." + args[0]) && "StringToCompare".equals(args[0])) {
// do something
}
} else {
// handle error
}

Multiple arguments for !somearray.contains

Is it possible to have multiple arguments for a .contains? I am searching an array to ensure that each string contains one of several characters. I've hunted all over the web, but found nothing useful.
for(String s : fileContents) {
if(!s.contains(syntax1) && !s.contains(syntax2)) {
found.add(s);
}
}
for (String s : found) {
System.out.println(s); // print array to cmd
JOptionPane.showMessageDialog(null, "Note: Syntax errors found.");
}
How can I do this with multiple arguments? I've also tried a bunch of ||s on their own, but that doesn't seem to work either.

No, it can't have multiple arguments, but the || should work.
!s.contains(syntax1+"") || !s.contains(syntax2+"") means s doesn't contain syntax1 or it doesn't contain syntax2.
This is just a guess but you might want s contains either of the two:
s.contains(syntax1+"") || s.contains(syntax2+"")
or maybe s contains both:
s.contains(syntax1+"") && s.contains(syntax2+"")
or maybe s contains neither of the two:
!s.contains(syntax1+"") && !s.contains(syntax2+"")
If syntax1 and syntax2 are already strings, you don't need the +""'s.
I believe s.contains("") should always return true, so you can remove it.

It seems that what you described can be done with a regular expression.
In regular expression, the operator | marks you need to match one of several choices.
For example, the regex (a|b) means a or b.
The regex ".*(a|b).*" means a string that contains a or b, and other then that - all is OK (it assumes one line string, but that can be dealt with easily as well if needed).
Code example:
String s = "abc";
System.out.println(s.matches(".*(a|d).*"));
s = "abcd";
System.out.println(s.matches(".*(a|d).*"));
s = "fgh";
System.out.println(s.matches(".*(a|d).*"));
Regular Exprsssions is a powerful tool that I recommend learning. Have a look at this tutorial, you might find it helpful.

There is not such thing as multiple contains.
if you require to validate that a list of string is included in some other string you must iterate through them all and check.
public static boolean containsAll(String input, String... items) {
if(input == null) throw new IllegalArgumentException("Input must not be null"); // We validate the input
if(input.length() == 0) {
return items.length == 0; // if empty contains nothing then true, else false
}
boolean result = true;
for(String item : items) {
result = result && input.contains(item);
}
return result;
}

Insertion into Hash Map data structure JAVA

I am using a program to read keywords in a file and sort them on basis of frequency. I am using Map data structure for the same.
But i am facing problem, even if i have repeated entries, their count is not increased. Thus if a word is repeated in the file it is stored in a different place in the data structure rather than incrementing value of the previous entry in the maps. Please find my code below. That is what i tried. Also i am making sure if a match is "" or " " it is not stored in the hash map still it is counted.
Pattern p = Pattern.compile("[a-zA-Z]*",Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(handlerContent);
while(m.find() ) //&& (m.group().length()>1)
{
boolean blnExists = keyword_counts.containsValue(m.group());
if(blnExists==true)
{
if(m.group()!="" || m.group()!=" ")
{
System.out.println("Repeat");
keyword_counts.put(m.group(), keyword_counts.get(m.group()+1));
System.out.println(m.group()+" "+keyword_counts.get(m.group()) );
}
}
else
{
if(m.group()!="" || m.group()!=" ")
{
keyword_counts.put(m.group(), 1);
System.out.println(m.group()+" "+keyword_counts.get(m.group()) );
}
}
}

Your test should probably be:
keyword_counts.containsKey(m.group());
And you should use equals to compare strings instead of == or != but that is not the reason for your issue.

in Java "=" should not be used with strings. use the "equals" method instead.

in your statement boolean blnExists = keyword_counts.containsValue(m.group());
you are check for the value instead of the key.
try this:
boolean blnExists = keyword_counts.containsKey(m.group());
and use if(m.group() != null && !"".equals(m.group().trim())) instead of
if(m.group()!="" || m.group()!=" ")