I am trying to remove every punctuation from my string: So far, I've done the following :
String line = "there's, isn't";
line.replaceAll("\\p{Punct}", "")
yet, this can't change "there's" into "theres" or "isn't" into "isnt".
I thought \p{Punct} includes every punctuation, including " ' " (as it's shown in api) yet this doesn't work. Can someone pls help?
Thanks in advance.
PS: expected outcome is: theres isnt
Strings are immutable in Java. String methods don't change the string in place, but instead return a modified copy of the string, so you need to assign the result back to the variable:
String line = "there's, isn't";
line = line.replaceAll("\\p{Punct}", "");
System.out.println(line); // theres isnt
As the previous answer said, the strings are immutable and once created you can't really change it. So once you code like String line = "there's, isn't";the string object "there's, isn't" will be created and line variable will be assigned to it. Java doesn't have the concept of pointers, but you can think of it as line variable pointing to the given string "there's, isn't". Now your next line line.replaceAll("\\p{Punct}", "") returns a newly created string object. You can assign it to another variable, say line_cleared=line.replaceAll("\\p{Punct}", "" and print that out: So here is the fully updated code:
String line = "there's, isn't";
line_cleared= line.replaceAll("\\p{Punct}", "");
System.out.println(line_cleared);
Related
I have a string which is :
1|name|lastname|email|tel \n
2|name|lastname|email|tel \n
I know that I have to use a loop to display all lines but the problem is that in my assignment
I can't use arrays or other classes than String and System.
Also I would like to sort names by ascending order without using sort method or arrays.
Do I have to use compareTo method to compare two names ?
If that's the case, how do I use compareTo method to sort names.
For example, if compareTo returns 1, that means that the name is greater than the other one. In that case how do I manage the return to sort name properly in the string ?
To display all substrings of the string as in the example, you can just go through all characters one by one and store them in a string. Whenever you hit a delimiter (e.g. | or \n), print the last string.
Here's a thread on iterating through characters of a string in Java:
What is the easiest/best/most correct way to iterate through the characters of a string in Java?
If you also need to sort the names in ascending order without an array, you will need to scan the input many times - sorting N strings takes at least N*log(N) steps. If this is a data structure question, PriorityQueue should do the trick for you - insert all substrings and then pop them out in a sorted fashion :)
building on the previous answer by StoneyKeys, since i do not have the privilege to comment, you can use a simple if statement that when the char is a delimiter, System.out.println() your previous scanned string. Then you can reset the string to an empty string in preparation for scanning the next string.
In java, there are special .equals() operators for strings and chars so when you won't be using == to check strings or char. Do look into that. To reset the value of string just assign it a new value. This is because the original variable points at a certain string ie "YHStan", by making it point at "", we are effectively "resetting" the string. ie scannedstr = "";
Please read the code and understand what each line of code does. The sample code and comments is only for your understanding, not a complete solution.
String str ="";
String value = "YH\nStan";
for (int i=0; i <value.length(); i++) {
char c = value.charAt(i);
String strc = Character.toString(c);
//check if its a delimiter, using a string or char .equals(), if it is print it out and reset the string
if (strc.equals("\n")) {
System.out.println(str);
str ="";
continue; // go to next iteration (you can instead use a else if to replace this)
}
//if its not delimiter append to str
str = str +strc;
//this is to show you how the str is changing as we go through the loop.
System.out.println(str);
}
System.out.println(str); //print out final string result
This gives a result of:
Y
YH
YH
S
St
Sta
Stan
Stan
I'm trying to read the title from a webpage and save it as a String. However, since Strings are immutable in java, I can't just set it to null and change it when I need to. Therefore, I'm getting an error on the next to last line that strTitle may not have been initialized. This seems like it should be easy to deal with, but I can't figure it out. Thanks in advance.
URL allRecipe = new URL(inputLine); //user defined url
BufferedReader urlIn = new BufferedReader(
new InputStreamReader(allRecipe.openStream()));
String inputFromWeb;
//loops through webpage and finds title
while((inputFromWeb = urlIn.readLine()) != null){
//getting title
if(inputFromWeb.contains("<title>")){
strTitle = urlIn.readLine();
}
}//end while
urlIn.close();
//print out title
System.out.println("Title:");
System.out.println(strTitle); //this line returns the error
System.out.println("\n");
since strings are immutable in java and I can't just set it to null
and change it when I need to.
Sure you can. If you are initializing a String reference to null and then assigning to it a different String, you are not changing any String, you are just changing the String reference.
However, as is I'm getting an error on the next to last line that
strTitle may not have been initialized.
String strTitle = null;
will solve your problem.
I have this code
String speed_string = "baka baka saka laka";
String[] string_array = speed_string.split(" ");
System.out.println(string_array.length);
and it returns the value of 1 when I run it. Why is that? It seems as if only the first word of the string gets saved.
Use \\s and update the code as below
String speed_string = "baka baka saka laka";
String[] string_array = speed_string.split("\\s");
System.out.println(string_array.length);
Most probably what you think is space (ASCII decimal 32) is not (in your input string).
That would explain perfectly the behavior you're seeing.
I've ran into a bit of a confusion.
I know that String objects are immutable. This means that if I call a method from the String class, like replace() then the original contents of the String are not altered. Instead, a new String is returned based on the original. However the same variable can be assigned new values.
Based on this theory, I always write a = a.trim() where a is a String. Everything was fine until my teacher told me that simply a.trim() can also be used. This messed up my theory.
I tested my theory along with my teacher's. I used the following code:
String a = " example ";
System.out.println(a);
a.trim(); //my teacher's code.
System.out.println(a);
a = " example ";
a = a.trim(); //my code.
System.out.println(a);
I got the following output:
example
example
example
When I pointed it out to my teacher, she said,
it's because I'm using a newer version of Java (jdk1.7) and a.trim()
works in the previous versions of Java.
Please tell me who has the correct theory, because I've absolutely no idea!
String is immutable in java. And trim() returns a new string so you have to get it back by assigning it.
String a = " example ";
System.out.println(a);
a.trim(); // String trimmed.
System.out.println(a);// still old string as it is declared.
a = " example ";
a = a.trim(); //got the returned string, now a is new String returned ny trim()
System.out.println(a);// new string
Edit:
she said that it's because I'm using a newer version of java (jdk1.7) and a.trim() works in the previous versions of java.
Please find a new java teacher. That's completely a false statement with no evidence.
Simply using "a.trim()" might trim it in memory (or a smart compiler will toss the expression entirely), but the result isn't stored unless you precede with assigning it to a variable like your "a=a.trim();"
String are immutable and any change to it will create a new string. You need to use the assignment in case you want to update the reference with the string returned from trim method. So this should be used:
a = a.trim()
You have to store string value in same or different variable if you want some operation (e.g trim)on string.
String a = " example ";
System.out.println(a);
a.trim(); //output new String is not stored in any variable
System.out.println(a); //This is not trimmed
a = " example ";
a = a.trim(); //output new String is stored in a variable
System.out.println(a); //As trimmed value stored in same a variable it will print "example"
This question already has answers here:
Java String replace not working [duplicate]
(6 answers)
Closed 9 years ago.
I got a query, please see code below:
public void readFile(String path,String pathName,int num){
try{
PrintWriter out2=new PrintWriter(new PrintWriter(path));
File a=new File(pathName);
Scanner b=new Scanner(a);
while(b.hasNextLine()){
String message=b.nextLine();
Scanner h=new Scanner(message);
while(h.hasNext()){
String f=h.next();
if (f.equals("are")){
f.replace("are","ARE");
}
}
out2.printf("%s",message);
out2.println();
.......
The file content for scanner read is
who are you?
how are you?
what is up!
However, when I run the above codes and the output to the new file are the same with the input file, it means the "are" not replaced by "ARE", I have no idea which part is wrong, please advise, thanks guys!
This line just outputs the message unchanged to the new file.
out2.printf("%s",message);
Also the loop is strange too: why do you read it word by word, and then use String.replace()? You could do it line by line, using String.replaceAll():
while(h.hasNextLine()){
String message=b.nextLine();
out2.printf("%s",message.replaceAll("(^|\\W)are(\\W|$)"," ARE "));
}
The (^|\\W)are(\\W|$) string is a regular expression, having the meaning to match all content, that starts with either being the start of the string ^, or a non-word character (\\W), the string are, and ends with a non-word character or the end of line($)...
As scanner has whitespace as the default delimiter, it might be ever better to use (^|\\s)are(\\s|$), however both these will replace the whitespace before and after "ARE" with a single space ()...
Also, keep in mind, that String.replace does not mutate the input String... You have to assign the result, or use it any other way, like pass it to a function...
String is final and immutable, which is the same.
so f.replace("are","ARE"); must be inserted into a new or not variable.
f = f.replace("are","ARE");
I do not understand why you are doing that. Here is an alternative approach:
Get a BufferedReader to read the file.
While there is data in the file, read the lines.
If line.contains("are") then line = line.replace("are","ARE")
println(line)
As to why your code did not work:
In this line, f.replace("are","ARE"); You forgot to get the output.
Make it as such: message = f.replace("are","ARE");
Another option is to use StringBuffer or StringBuilder
Strings are immutable. Therefore, you can not run the replace method on object f and expect its value to be changed since the replace method of a string object will simply return a new String object.
either use a StringBuilder instead, or use :
f = f.replace
On the other hand, StringBuilder objects are mutable. Therefore, you can run the StringBuilder version of the replace method directly on the object if you choose that route instead.