Remove first line java

Java remove first line from string python

Mentioned below is a code snippet Solution: should do the trick Solution 1: overriding TextArea’s replaceText method and a check for line count than delete first line if it exeeds 20 lines seems working, Solution 2: If u means that new line is \n this code will works fine. Solution 2: use to read line by line , just ommit first line and consider others in processing Solution 3: Thanks for the inputs.

How to remove first line and last line in a String in android

If it is stored in a String you can simply call

String [] strArr = str.split("\\n"); 

now ignore strArr[0] and strArr[strArr.length-1], and get the rest.

If its static you could do this :

key = key.replace("-----BEGIN PUBLIC KEY-----", ""); key = key.replace("-----END PUBLIC KEY-----", ""); 

if its not you could use the split() method on \n maybe and then just keep the center string

as this «——BEGIN PUBLIC KEY——» and this «——END PUBLIC KEY——» are alwayes have constant length you can use substring.

String key = "-----BEGIN PUBLIC KEY-----" + "MIGeMA0GCSqGSIb3DQEBAQUAA4GMADCBiAKBgE0JOa5WUcifbDnnQWB2WKOOODwq" + "JUxu/7fG2BaynwVRSifljrzGjqpS24R0ss3cZZSKfD2GszG0aVd5T1Yvh4kSOzsx" + "arj8QUkfW/EL5ClhDv8LVtkErbTU42QLUUTl5izyKZXaHFdBnJZ8jqXk4AlK22mp" + "LcMadrpv7SzQJq1HAgMBAAE=" + "-----END PUBLIC KEY-----"; String result; result = key.substring(26,key.length()-24); 

Hide/Remove first line from total address block in JSP, I was calling a method as given here — to print the total address block. Address add = AddressManager.getMyAddress(someId); String totalAddr =

Remove first line from delimited file

Don’t delete it, just read-and-ignore .

If you have to prepare the file because the file processing units can’t handle a file with an incorrect first line, then you’ll have to read and rewrite it. There is no I/O operation available that can delete contents from file in the filesystem .

use readLine() to read line by line , just ommit first line and consider others in processing

Thanks for the inputs. Depending on the same , I figured out a solution to remove the first line from the delimited pipe file.

Mentioned below is a code snippet

RandomAccessFile raf = new RandomAccessFile("path to ur delimited file", "rw"); FileChannel fileChannel = raf.getChannel(); raf.readLine(); raf.seek(raf.getFilePointer()); int len = (int) (raf.length() - raf.getFilePointer()); byte[] bytearr = new byte[len]; raf.readFully(bytearr, 0, len); fileChannel.truncate(0); raf.write(bytearr,0,len); 

Python — Remove first element of list, This is a lesser-known method to achieve this particular task, converting the list into deque and then performing the pop left, removes the

Removing first line from string in Groovy

def soapBodyList = new File(inputFilename).readLines() return soapBodyList[1..soapBodyList.size-1].join("") 

Remove first 32 characters from first line in file, My goal is to strip the first 32 characters of the first line of this file, then overwrite the line. My code (below) successfully grabs the

Delete first Line of a JavaFx Textarea

overriding TextArea’s replaceText method and a check for line count than delete first line if it exeeds 20 lines seems working,

import javafx.application.Application; import javafx.scene.Scene; import javafx.scene.control.TextArea; import javafx.scene.layout.StackPane; import javafx.stage.Stage; public class FixedLineCountTextAreaTry extends Application < public static void main(String[] args) < launch(args); >@Override public void start(Stage primaryStage) < primaryStage.setTitle("Try to enter me more than 20 lines. "); TextArea ta = new TextArea() < @Override public void replaceText(int start, int end, String text) < super.replaceText(start, end, text); while(getText().split("\n", -1).length >20) < int fle = getText().indexOf("\n"); super.replaceText(0, fle+1, ""); >positionCaret(getText().length()); > >; StackPane root = new StackPane(); root.getChildren().add(ta); primaryStage.setScene(new Scene(root, 300, 500)); primaryStage.show(); > > 

If u means that new line is \n this code will works fine.

 String array[] = textArea.getText().split("\n"); String textToSet = ""; for(int i=1; i textArea.setText(textToSet); 

Try this solution based on a text formatter.

TextFormatter  < change ->if (change.isAdded) < val maxByteSize = 1.5e+6 //15 mb if (change.controlNewText.length change.text.length) change.text.length else textArea.length textArea.replaceText(0, end, "") change.setRange(textArea.length, textArea.length) change > > else < change >> 

How can I remove \n from a string without translate, replace or strip, I’m trying to read the txt file one line at a time and then the value of that line would become one of the variables for the player stats. If I

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JTextPane removing first line

I get Document object from JTextPane , which contains method remove , but specific number of chars textPane.getDocument().remove(begin,end) . I would like to remove whole first line.

3 Answers 3

The following shows how to remove the first line (Element) of a JTextPane if you are considering lines «things that end in a newline». If you have fancier content in your Document, you may need to do something more elaborate

JTextPane pane = new JTextPane(); pane.setText("I've got to go\nI can stay, though.\nThree lines of text?"); System.out.println(pane.getText()); System.out.println("\n\n\n removing! \n\n\n"); Element root = pane.getDocument().getDefaultRootElement(); Element first = root.getElement(0); pane.getDocument().remove(first.getStartOffset(), first.getEndOffset()); System.out.println(pane.getText()); 

See Limit Lines in Document. The code in that class will show you how to get the start/end offsets of the characters in the line.

Or you can use the Utilities class.

Once you know the start/end you can use the remove() method.

How are you creating the String that goes in the first line? If the code telling the JTextPane what string to write is based off an existing String variable like below

private String myString = "Hello, this is the first line!"; private JTextPane myPane = new JTextPane(. ); . public void writeFirstLine()

then you can do the following:

textPane.getDocument().remove(0, myString.length()); //this is assuming the remove function //excludes the end index and removes everything up to it. Otherwise, it would be //myString.length()-1 

if you don’t have the first line pre-defined as above and you basically just want to remove up to the first period or other special character, you can use a StreamTokenizer to find the target separating character (which can be the end of a line [EOL] with EOL set to significant. You can set whitespace to significant in a streamtokenizer and add them as soon as they are encountered to a character counter variable. Then you would essentially cast each token to string inside an initially null String object (that you re-use for each token) before allowing the streamtokenizer to move on and obtain the character length of each, adding it to the character counter variable before moving on to the next token. When the separator punctuation character is reached, run the addition operation once more for the last token, and then your character counter variable will have the number of characters up to the end of the first line. In this case, the code would be:

textPane.getDocument().remove(0,charCounter) //this is assuming the remove function //excludes the end index and removes everything up to it. Otherwise, it would be charCounter-1 

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Fastest Java way to remove the first/top line of a file (like a stack)

I am trying to improve an external sort implementation in java. I have a bunch of BufferedReader objects open for temporary files. I repeatedly remove the top line from each of these files. This pushes the limits of the Java’s Heap. I would like a more scalable method of doing this without loosing speed because of a bunch of constructor calls. One solution is to only open files when they are needed, then read the first line and then delete it. But I am afraid that this will be significantly slower. So using Java libraries what is the most efficient method of doing this. —Edit— For external sort, the usual method is to break a large file up into several chunk files. Sort each of the chunks. And then treat the sorted files like buffers, pop the top item from each file, the smallest of all those is the global minimum. Then continue until for all items. http://en.wikipedia.org/wiki/External_sorting My temporary files (buffers) are basically BufferedReader objects. The operations performed on these files are the same as stack/queue operations (peek and pop, no push needed). I am trying to make these peek and pop operations more efficient. This is because using many BufferedReader objects takes up too much space.

Can you be more specific about what your implementation is actually doing and how the algorithm is intended to operate? This is unclear to me as written.

I think what was blowing up the heap space is because I had a wrapper around the BufferedReaders. I was inserting these into a Priority Queue. Instead I am going to make a smaller index class to put in the priority queue to see if it helps.

@chrisangrant — A Java profiler would tell you exactly what’s using up all the memory. I’ve had great experiences using YourKit Java Profiler.

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How to remove first line of a text file in java [duplicate]

I am trying to find a way to remove the first line of text in a text file using java. Would like to use a scanner to do it. is there a good way to do it without the need of a tmp file? Thanks.

For many uses, you should always use a temp file on the same partition, then use rename/move operation of the OS to atomically replace old file with the new, so the file is never only partially written.

4 Answers 4

If your file is huge, you can use the following method that is performing the remove, in place, without using a temp file or loading all the content into memory.

public static void removeFirstLine(String fileName) throws IOException < RandomAccessFile raf = new RandomAccessFile(fileName, "rw"); //Initial write position long writePosition = raf.getFilePointer(); raf.readLine(); // Shift the next lines upwards. long readPosition = raf.getFilePointer(); byte[] buff = new byte[1024]; int n; while (-1 != (n = raf.read(buff))) < raf.seek(writePosition); raf.write(buff, 0, n); readPosition += n; writePosition += n; raf.seek(readPosition); >raf.setLength(writePosition); raf.close(); > 

Note that if your program is terminated while in the middle of the above loop you can end up with duplicated lines or corrupted file.

Scanner fileScanner = new Scanner(myFile); fileScanner.nextLine(); 

This will return the first line of text from the file and discard it because you don’t store it anywhere.

To overwrite your existing file:

FileWriter fileStream = new FileWriter("my/path/for/file.txt"); BufferedWriter out = new BufferedWriter(fileStream); while(fileScanner.hasNextLine()) < String next = fileScanner.nextLine(); if(next.equals("\n")) out.newLine(); else out.write(next); out.newLine(); >out.close(); 

Note that you will have to be catching and handling some IOException s this way. Also, the if(). else(). statement is necessary in the while() loop to keep any line breaks present in your text file.

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