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Write a procedure loadDocument(String name) which will load and analyze lines after lines searching for link in every line

Write a procedure loadDocument(String name) which will load and analyze lines after lines searching for link in every line. The link format is as follows: 5 characters link= (it can be mixed capital and small letters) after which there is a correct identifier. The correct identifier starts from letter (small or capital) follows by zero or more occurrences of letters or digits or underline _. The procedure has to print subsequent identifiers, each one in a separated line. Before printing, the identifiers have to be changed to small letters. The document ends with line with the text eod, which means end of document.
My code:
public static void loadDocument(String name, Scanner scan) {
while(scan.hasNext()) {
String line = scan.nextLine();
if(line.equals("eod")) {
return;
}
else if(line.matches("link="+name) && correctLink(name)) {
String identifier = name.toLowerCase();
System.out.println(identifier);
}
else
continue;
}
}
// accepted only small letters, capital letter, digits and '_' (but not on the begin)
public static boolean correctLink(String link) {
if(link.matches("^[a-zA-Z]+[0]+||[0-9]+||_"))
return true;
else
return false;
}
How to write if line equal to link=, return whatever's after link=?
My problem is in this code:
else if(line.matches("link="+name) && correctLink(name)) {
String identifier = name.toLowerCase();
System.out.println(identifier);
}
For example, if the input is link=abc, I want it to print abc.

First I would suggest that you get used to compare to literal strings "the other way round" - this will save you from a lot NullPointerExceptions (but this is just a side comment):
if ("eod".equals(line))
You can use #Ofer s example (it is generated from https://regex101.com, a nice page to play around with regular expressions and get them explained btw.) but you should use a different regex:
final String regex = "link=([a-z][a-z0-9_]*)";
and a different option for the pattern:
final Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);
I used the CASE_INSENSITIVE option to make the "link" also trigger for mixed case writings (like "Link", "liNk" and so on). Therefore I also could skip the uppercase letters from the actual regex, as [a-z] will also match uppercase letters with that option, and that's what was requested.
The "magic" here is that you put the expression that you later want to "read" from the pattern matcher into parenthesis "()" - this marks a "group". Group 0 always gives back the full match (including the "link=" here).
You can play around with that expression at https://regex101.com/r/id2CP2/1
Please don't forget to convert the identifiers (you get them from matcher.group(i)) to lowercase before you output them.

How can I check a string for multiple specific characters in java

I need to check a string to see if it contains any one of these characters (#, $, %, &) in java. I need to check for all 4 at the same time, with out a loop if possible and without regex. I am using this to verify validity of an email address so I cant just check for special characters as the email contains the #. Is there a way to use the .contains method with a switch statement?

Given a String str, and no loops or regular expressions you could presumable call String.contains(CharSequence) with a series of boolean ands like
if (str.contains("#") && str.contains("$") && str.contains("%")
&& str.contains("&")) {
System.out.printf("%s contains #$%%&%n", str);
} else {
System.out.printf("%s does not contain #$%%&%n", str);
}

You should use String.contains(...)

String.subString(String foo) allows you to search for specific case sensitive characters.
Foo.subString(String.ignoreCase("bar") will search foo for the string of characters "bar".
This will return the index of the first letter of "bar", and return -1 if the string is not found.

How to check if the first four characters of a string are A-G and the last 3 are numeric?

I have been poking around with this and I feel it might be best if the string (AAAA-123 or AAA123) be split up into 2 strings and compared. I can ensure they are all numeric characters but making sure they are in the right format and I dont feel that I must be missing something.
Name = txtfClass.getText();
if((Name.length()==8)&&(Name.matches("[a-gA-G]-\\d{3}"))){
checker(Name);
System.out.println("it works");
}
That code wont work when Name = ABCD-123. What is it that I'm missing? If you are wondering here checker(Name) goes:
public boolean checker(String name){
CourseAbrv = name.substring(0, 4);
System.out.println(CourseAbrv);
return false;
}
It returns nothing

Change your regex to Name.matches("[A-G]{4}-\\d{3}"). [a-gA-G] matches a Single character.
Note : This matches only capital A-G. You can use a-g instead of A-G to match only lowercase.

Comparing parts of Arrays against each other?

I'm really really really not sure what is the best way to approach this. I've gotten as far as I can, but I basically want to scan a user response with an array of words and search for matches so that my AI can tell what mood someone is in based off the words they used. However, I've yet to find a clear or helpful answer. My code is pretty cluttered too because of how many different methods I've tried to use. I either need a way to compare sections of arrays to each other or portions of strings. I've found things for finding a part of an array. Like finding eggs in green eggs and ham, but I've found nothing that finds a section of an array in a section of another array.
public class MoodCompare extends Mood1 {
public static void MoodCompare(String inputMood){
int inputMoodLength = inputMood.length();
int HappyLength = Arrays.toString(Happy).length();
boolean itWorks = false;
String[] inputMoodArray = inputMood.split(" ");
if(Arrays.toString(Happy).contains(Arrays.toString(inputMoodArray)) == true)
System.out.println("Success!");
InputMood is the data the user has input that should have keywords lurking in them to their mood. Happy is an array of the class Mood1 that is being extended. This is only a small piece of the class, much less the program, but it should be all I need to make a valid comparison to complete the class.
If anyone can help me with this, you will save me hours of work. So THANK YOU!!!

Manipulating strings will be nicer when you do not use the relative primitive arrays, where you have to walk through yourself etcetera. A Dutch proverb says: not seeing the wood through the trees.
In this case it seems you check words of the input against a set of words for some mood.
Lets use java collections:
Turning an input string into a list of words:
String input = "...";
List<String> sentence = Arrays.asList(input.split("\\W+"));
sentence.remove("");
\\W+ is a sequence of one or more non-word characters. Mind "word" mean A-Za-z0-9_.
Now a mood would be a set of unique words:
Set<String> moodWords = new HashSet<>();
Collections.addAll(moodWords, "happy", "wow", "hurray", "great");
Evaluation could be:
int matches = 0;
for (String word : sentence) {
if (moodWords.contains(word)) {
++matches;
}
}
int percent = sentence.isEmpty() ? 0 : matches * 100 / sentence.size();
System.out.printf("Happiness: %d %%%n", percent);
In java 8 even compacter.
int matches = sentence.stream().filter(moodWords::contains).count();
Explanation:
The foreach-word-in-sentence takes every word. For every word it checks whether it is contained in moodWords, the set of all mood words.
The percentage is taken over the number of words in the sentence being moody. The boundary condition of an empty sentence is handled by the if-then-else expression ... ? ... : ... - an empty sentence given the arbitrary percentage 0%.
The printf format used %d for the integer, %% for the percent sign % (self-escaped) and %n for the line break character(s).

If I'm understanding your question correctly, you mean something like this?
String words[] = {"green", "eggs", "and", "ham"};
String response = "eggs or ham";
Mood mood = new Mood();
for(String foo : words)
{
if(response.contains(foo))
{
//Check if happy etc...
if(response.equals("green")
mood.sad++;
...
}
}
System.out.println("Success");
...
//CheckMood() etc... other methods.

Try to use tokens.
Every time that the program needs to compare the contents of a row from one array to the other array, just tokenize the contents in parallel and compare them.
Visit the following Java Doc page for farther reference: http://docs.oracle.com/javase/7/docs/api/java/util/StringTokenizer.html
or even view the following web pages:
http://introcs.cs.princeton.edu/java/72regular/Tokenizer.java.html

match all characters in a string independent of their order in the sequence

I want to match certain group of characters in a String independent of their order in the String using regex fucntion. However, the only requirement is that they all must be there.
I have tried
String elD = "15672";
String t = "12";
if ((elD.matches(".*[" + t + "].*"))) {
System.out.println(elD);
}
This one checks whether any of the characters are present. But I want all of them to be there.
Also I tried
String elD = "15672";
String t = "12";
if ((elD.matches(".*(" + t + ").*"))) {
System.out.println(elD);
}
This does not work as well. I have searched quite a while but I could not find an example when all of the characters from the pattern must be present in the String independent of their order.
Thanks

You can write regex for this but it would not look nice. If you would want to check if your string contains anywhere x and y you would need to use few times look-ahead like
^(?=.*x)(?=.*y).*$
and use it like
yourStirng.matches(regex);
But this way you would need to create your own method which would generate you dynamic regex and add (?=.*X) for each character you want to check. You would also need to make sure that this character is not special in regex like ? or +.
Simpler and not less effective solution would be creating your own method which would check if your string contains all searched characters, something like
public static boolean containsUnordered(String input, String searchFor){
char[] characters = searchFor.toCharArray();
for (char c: characters)
if (!input.contains(String.valueOf(c)))
return false;
return true;
}

You can built a pattern from the search string using the replaceAll method:
String s = "12";
String pattern = s.replaceAll("(.)", "(?=[^$1]*$1)");
Note: You can't test the same character several times. (i.e. 112 gives (?=[^1]*1)(?=[^1]*1)(?=[^2]*2) that is exactly the same as (?=[^1]*1)(?=[^2]*2))
But in my opinion Pshemo method is probably more efficient.