I'm still new to Java and I would like to understand Strings and Arrays so I got this idea of manipulating elements and place them according to my objective. The objective is that there will be Array of Strings "ABBCCCBBAA" and the "AA","BB" must be replaced into "A" , "BA","AB" into CC. "CC","BC" into B. I basically have no idea how to make it happen but I know it must have Arrays of String. Please help
Regular expression can be very handy for you. Code bellow can do, your job with the use of regular expression:
String mainStr = "ABBCCCBBAA";
Pattern p = Pattern.compile("(AA)|(BB)|(BA)|(AB)|(CC)|(BC)");
Matcher m = p.matcher(mainStr);
while (m.find()) {
String matchedStr = m.group(0);
if("AA".equals(matchedStr) || "BB".equals(matchedStr)){
mainStr = mainStr.replaceFirst(matchedStr,"X");
}
else if("BA".equals(matchedStr) || "AB".equals(matchedStr)){
mainStr = mainStr.replaceFirst(matchedStr,"Y");
}
else if("CC".equals(matchedStr) || "BC".equals(matchedStr)){
mainStr = mainStr.replaceFirst(matchedStr,"Z");
}
}
mainStr = mainStr.replaceAll("X","A").replaceAll("Y","CC").replaceAll("Z","B");
System.out.println(mainStr);
Above code will handle your case of multiple occurrence of same pattern in a given string like:
ABBCCCBBAABBBBAA
will generate output:
CCBBAAAAA.
I am assuming that by "array of strings" you mean:
String[] myvariable = new String[number];
myvariable[0] = "ABBCCBBAA";
myvariable[1] = "some_other_string";
If you are new to Java I suggest you read a beginner's book like Head First Java and also look into java documentation; you don't even have to go that far if you are programming with a decent IDE, like Netbeans (thanks to its intelli-sense feature) is a source of documentation for what you seek (meaning that you can look at all the methods available for a string, read what they do, and see if they can help accomplish what you need).
I am assuming (from what you have said) that you want to replace "AA" for "A", and from that result replace "BB" for "BA", and from that result replace "AB" into "CC", and from that result "BC" into "B".
The code I am posting is REAL simple, and it will only work for this particular case (as I have understood it), if you want to create a method that does this for any string, you need to change some things, but I'll leave that to you.
String[] yourArrayOfStrings = new String[1];
yourArrayOfStrings[0] = "ABBCCBBAA";
String resultOfReplacement= yourArrayOfStrings[0].replaceFirst("AA", "A");
System.out.println(resultOfReplacement); //debugging purposes
resultOfReplacement = resultOfReplacement.replaceFirst("BB", "BA");
System.out.println(resultOfReplacement); //debugging purposes
resultOfReplacement = resultOfReplacement.replaceFirst("AB", "CC");
System.out.println(resultOfReplacement); //debugging purposes
resultOfReplacement = resultOfReplacement.replaceFirst("BC", "BB");
System.out.println(resultOfReplacement); //debugging purposes
The only reason why I created a String[] was because that's what you stated in your question, otherwise I would have simple created a String variable like I did with resultOfReplacement. To access the first element in an array you do arrayVariable[index]. Here I use the replaceFirst function that comes with Java for variables of type String. If you look the method up, it'll tell you that it will look for the first match of the first parameter and replace it with the second parameter.
The System.out.println I have added are for debugging purposes, so you can see on the console what is clearly happening with each replacement. So, the first time I call replaceFirst(...) on the original string which is a[0].
This will happen:
The method will look in "ABBCCBBAA" for the FIRST AND ONLY THE FIRST time "AA" appears and replace it with "A". The result is "return" and you must assign it to a variable if you want access to it to do more actions upon it. In this case, I assign it to a new String variable. You could have just assigned back to a[0], which is likely what you want. (You'd do so like this: a[0]=ourArrayOfStrings[0].replaceFirst("AA", "A");)
For the second replacement, the method will look in "ABBCCBBA" for the first time "BB" appears and replace it for "BA".
See the pattern? This is just a start, and depending on what you want you might need other methods like replaceAll().
Most IDEs will tell you what methods are available for a variable when you access it via ".", so that when you are typing " variablename. " right at that moment a list of methods available for it should appear, if they don´t you can go ahead and do a shortcut like ctrl+space for it to appear and navigate through the methods via the arrow keys so you can read what they do (at least for Eclpise and Netbeans, while programming in Java, it works). Documentation is power!
Related
I have a string that needs to be compared to the names that are on the website. So the first thing I do is get the number of rows (because some arrays have more or fewer than 2 people in them) and then put that size into an int. String[] names come from the names that selenium is supposed to find when it goes to the website to execute this statement assertTrue(assertion.getText().contains(names[i-1])); The problem is: if the names do not appear in the order in which they appear in the array it breaks. In other words, if Mick Jagger is in li[1] and Keith Richards is in li[2], everything runs as expected. But if Keith Richards appears in li[1] it breaks. Furthermore, I am supposed to use the assertTrue command to do this. I have tried sorting, pushing whats on the web into a new ArrayList and I keep getting errors. Anyone know a good way to ensure the order isn't important and still use the assertTrue command?
Thanks,
Scott
WebElement assertion = null;
List<WebElement> assignees = driver.findElements(By.xpath(".//*[#id='assignee']/li"));
int count = assignees.size();
String[] names = {"Mick", "Keith"};
for (int i = 1; i < count; i++)
{
assertion = driver.findElement(By.xpath(".//*[#id='assignee']/li["+i+"]"));
assertTrue(assertion.getText().contains(names[i-1]));
If names represents the full string, you can just flip it. Make sure the text in your assertion (probably should be named something like assignee instead of assertion) is contained in your collection:
assertTrue(Arrays.asList(names).contains(assertion.getText());
Let me know if this won't work because a name is actually a subset of the text in assertion and I'll adjust the answer.
If they don't exactly match (which you have indicated they don't), you could use linq in c# to match this. Since you're using java you can use an additional loop. There may be a more efficient way to do this in java that I'm not aware of.
String assigneeText = assertion.getText();
boolean nameFound = false;
for(String name: names)
{
nameFound = assigneeText.contains(name);
if(nameFound)
{
break;
}
}
assertTrue(nameFound, "None of the expected names were found in the following assignee text: " + assigneeText);
I'm learning Java, and I'm completing some problems tasked to me.
I've come across a specific problem and I feel like the answer is so simple, but I just can't find it.
I need to check if given string ends with the first two characters it begins with. For example, "edited" (begins and ends with "ed")
I've tried using the java endsWith and startsWith, but I keep getting an error
start = text.startsWith(text.substring(0,2));
Yeilds
Error: incompatible types
required: java.lang.String
found: boolean
Any help would be appreciated.
Thankyou.
You're calling startsWith when you don't need to - you know it starts with the first two characters, by definition :)
You could have:
String start = text.substring(0, 2);
boolean valid = text.endsWith(start);
Or just collapse the two:
boolean valid = text.endsWith(text.substring(0, 2));
I'm assuming you already know the string is of length 2 or more... if not, you should check that first. (And change the variable valid to whatever makes sense in your context.)
This is a dynamic code for what you need to do
let's say we have
String testak = "tesHJKLtes"
//index you need to check here 2
int ind = 2;
ind is the index you need to check
if ( testak.substring(0,ind).equals(testak.substring(testak.length()
-ind-1,testak.length()-1))){
System.out.println("yeeaaahhh");
}
and consider that this you are not limited to 2 anymore you can give ind any number you like
and it will work
This is probably a simple one and more Java related than grails but I'm a bit lost and not sure where to even start looking on this, I've googled about but am not really sure what I'm after, so would appreciate a pointer if possible please!
In the grails app I have a form which I save, all well and good. In the controller I can see the list of params it returns via a simple println and when I want to find a specific value currently I do a params.each and then compare the key to a pre defined string to find the one I want, my question is: -
Can I, and how would I, specifically say "get me the value of the parameter with the key "banana", rather than having to loop through the whole list to find it?
Also is there a way of creating a new set of secondary params, or just another plain old dictionary item (is that the right term?) where I use a regular expression to say "give me all the items whose key match the pattern "XYZ"?
It probably doesn't make much difference speed wise as the params are never that big but it'd be nice to make things more efficient where possible.
Any feedback much appreciated!
For a first question, to get 'banana' parameter you have to use:
params.banana
For second, find all with regexp:
def matched = params.findAll { it.key =~ /XYZ/ }
//or
Pattern p = ~/XYZ/
def matched = params.findAll { p.matcher(it.key).matches() }
There's a params object you can use. Eg with someurl.com?myparam=test you can access it with "params.myparam"
More information over here: http://grails.org/doc/2.2.x/ref/Controllers/params.html
I asked about this array a little while ago, and I can't see what the problem is. Too tired. What have I done wrong? Basically, I am taking a string array and trying to check to see if it contains numbers or an x (ISBN number validation). I want to take the number from a given input (bookNum), check the input, and feed any valid input into a new array (book). At the line
'bookNum.charAt[j]==book[i]'
I get the 'not a statement error'. What gives?
String[] book = new String [ISBN_NUM];
bookNum.replaceAll("-","");
if (bookNum.length()!=ISBN_NUM)
throw new ISBNException ("ISBN "+ bookNum + " must be 10 characters");
for (int i=0;i<bookNum.length();i++)
{
if (Character.isDigit(bookNum.charAt(i)))
bookNum.CharAt[j]==book[i];
j++;
if (book[9].isNotDigit()||
book[9]!="x" ||
book[9]!="X")
throw new ISBNException ("ISBN " + bookNum + " must contain all digits" +
"or 'X' in the last position");
== is java is used for equivalence comparison. If you want to assign it, use a single =.
The first issue here is that charAt is a function, and thus needs parenthesis even though you are accessing with an index like an array.
The other issue is that the line is a boolean expression, which just by itself does not mean anything. A lot of people are suggestion that you mean to make an assignment to that character, but just changing to a single equals causes other problems. The left side of an equals sign needs to be a variable, and the result of a function is not a variable.
Strings are immutable, so you can not simply change one of the characters in the string. Earlier in your code, you have a call to replaceAll(), that returns a new string with the alterations. As written, this altered string is being lost.
There are few odd problems here. For starters, did you mean for book to be an array of Strings, as opposed to just one string? You're trying (assuming CharAt was written properly and the assignment was proper) to assign a character to a string.
Second, instead of copying character by character, why not check the whole string, and copy the whole thing at the end if it is a proper ISBN? Depending on what you do with Exceptions (if you continue regardless), you could add a boolean as a flag that gets set if there is an error. At the end, if there is no error, then make book = to booknumber.replace(etc...)
bookNum.CharAt[j]==book[i];
Should be
bookNum.CharAt[j]=book[i];
You are using an equality boolean operator, not an assignment one.
Looks like you're using .charAt(i) wrong! Assuming that "bookNum" is a String, you should use:
bookNum.charAt(i)==book[i];
Instead. Note that this is a boolean expression, and not "=".
The line bookNum.CharAt[j]==book[i]; isn't a statement. It's a comparison. Perhaps you want bookNum.CharAt[j]=book[i]; (single = instead of ==).
Edit: That's not going to fix things, though, since you can't assign to bookNum.CharAt[j].
This question already has answers here:
How to format strings in Java
(10 answers)
Closed 5 years ago.
Is there a more elegant way of doing this in Java?
String value1 = "Testing";
String test = "text goes here " + value1 + " more text";
Is it possible to put the variable directly in the string and have its value evaluated?
String test = String.format("test goes here %s more text", "Testing");
is the closest thing that you could write in Java
A more elegant way might be:
String value = "Testing";
String template = "text goes here %s more text";
String result = String.format(template, value);
Or alternatively using MessageFormat:
String template = "text goes here {0} more text";
String result = MessageFormat.format(template, value);
Note, if you're doing this for logging, then you can avoid the cost of performing this when the log line would be below the threshold. For example with SLFJ:
The following two lines will yield the exact same output. However, the second form will outperform the first form by a factor of at least 30, in case of a disabled logging statement.
logger.debug("The new entry is "+entry+".");
logger.debug("The new entry is {}.", entry);
Rythm a java template engine now released with an new feature called String interpolation mode which allows you do something like:
String result = Rythm.render("Hello #who!", "world");
The above case shows you can pass argument to template by position. Rythm also allows you to pass arguments by name:
Map<String, Object> args = new HashMap<String, Object>();
args.put("title", "Mr.");
args.put("name", "John");
String result = Rythm.render("Hello #title #name", args);
Links:
Check the full featured demonstration
read a brief introduction to Rythm
download the latest package or
fork it
It may be done by some template-libaries. But beware, Strings are immutable in Java. So in every case at some low level the concatenation will be done.
You'll always have to use some form of concatenation for this (assuming value1 isn't a constant like you show here).
The way you've written it will implicitly construct a StringBuilder and use it to concatenate the strings. Another method is String.format(String, Object...)1, which is analogous to sprintf from C. But even with format(), you can't avoid concatenation.
1 Yes, I know the anchor link is broken.
What you want is called String interpolation. It is not possible in Java, although JRuby, Groovy and probably other JVM languages do that.
Edit: as for elegance, you can use a StringBuffer or check the other poster's solution. But at the low level, this will always be concatenation, as the other posters said.
You can use this free library. It gives you sprintf like functionality. Or use String.format static method provided you use Java 5 or newer.
Why do you think string concatenation isn't elegant?
If all you are doing is simple concatenation, I'd argue that code readability is more important and I'd leave it like you have it. It's more readable than using a StringBuilder.
Performance won't be the problem that most people think it is.
Read this from CodingHorror
I would use a StringBuffer.. it's a common practise when you are dealing with strings. It may seem a bit when you see it for the first time, but you'll get quickly used to it..
String test = new StringBuffer("text goes here ").append(value1).append(" more text").toString();
Strings are immutable thus a new instance is created after every concatenation. This can cause performance issues when used in loops.
StringBuffer is mutable version of String - that means you can create one, modify it as you want and you have still only one instance. When desired you can get a String representation of the StringBuffer by calling it's toString() method.
The problem is not if this is an elegant way or not. The idea behind using a template system may be that you put your template in a normal text file and don't have to change java code if you change your message (or think about i18ln).