Java - LineNumberReader skip(long n) method

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Description

The Java LineNumberReader skip(long n) method skips l characters from the input stream while keeping track of line numbers. It does not skip full lines but individual characters, including newlines (\n), which can affect the line number count.

Declaration

Following is the declaration for java.io.LineNumberReader.skip(long n) method −

public long skip(long n)

Parameters

n − The number of characters to skip.

Return Value

The number of characters actually skipped.

Exception

• IOException − If an I/O error occurs.

• IllegalArgumentException − If n is negative.

Example - Usage of LineNumberReader skip(long n) method

The following example shows the usage of Java LineNumberReader skip(long n) method.

LineNumberReaderDemo.java

package com.tutorialspoint;

import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;

public class LineNumberReaderDemo {
   public static void main(String[] args) throws IOException {
      FileReader fr = null;
      LineNumberReader lnr = null;
      int i;
      char c;
      
      try {
         // create new reader
         fr = new FileReader("test.txt");
         lnr = new LineNumberReader(fr);
   
         // read till the end of the stream
         while((i = lnr.read())!=-1) {
         
            // skip one byte
            lnr.skip(1);
            
            // converts integer to char 
            c = (char)i;
            
            // prints char
            System.out.print(c);
         }
         
      } catch(Exception e) {
         // if any error occurs
         e.printStackTrace();
      } finally {
         // closes the stream and releases system resources
         if(fr!=null)
            fr.close();
         if(lnr!=null)
            lnr.close();
      }
   }
}

Output(Assuming test.txt contains "ABCDE")

Let us compile and run the above program, this will produce the following result−

ACE

Example - Skipping Characters and Tracking Line Numbers

The following example shows the usage of Java LineNumberReader skip(long n) method. This example skips 6 characters from the input and then reads the next line.

LineNumberReaderDemo.java

package com.tutorialspoint;

import java.io.IOException;
import java.io.LineNumberReader;
import java.io.StringReader;

public class LineNumberReaderDemo {
   public static void main(String[] args) {
      String text = "Hello\nWorld\nJava Programming";
      LineNumberReader lnr = new LineNumberReader(new StringReader(text));

      try {
         System.out.println("Reading first character: " + (char) lnr.read());

         // Skip 6 characters
         lnr.skip(6);
         System.out.println("After skipping 6 characters, next character: " + (char) lnr.read());

         System.out.println("Current Line Number: " + lnr.getLineNumber());

         lnr.close();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output(if example.txt contains "HelloWorld")

Let us compile and run the above program, this will produce the following result−

Reading first character: H
After skipping 6 characters, next character: W
Current Line Number: 1

Explanation

• Reads the first character (H).

• Skips 6 characters, which includes "ello\nW".

• Reads the next character, which is W from "World".

• Line number updates to 1 because a newline (\n) was skipped.

Example - Skipping Over Multiple Lines

The following example shows the usage of Java LineNumberReader skip(long n) method. This example skips characters across multiple lines and checks how the line number changes.

LineNumberReaderDemo.java

package com.tutorialspoint;

import java.io.IOException;
import java.io.LineNumberReader;
import java.io.StringReader;

public class LineNumberReaderDemo {
   public static void main(String[] args) {
      String text = "First Line\nSecond Line\nThird Line";
      LineNumberReader lnr = new LineNumberReader(new StringReader(text));

      try {
         System.out.println("Initial Line Number: " + lnr.getLineNumber());

         // Skip first 12 characters, including '\n'
         lnr.skip(12);
         System.out.println("After skipping 12 characters, next character: " + (char) lnr.read());

         System.out.println("Line Number After Skip: " + lnr.getLineNumber());

         lnr.close();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Initial Line Number: 0
After skipping 12 characters, next character: S
Line Number After Skip: 1

Explanation

• Line number starts at 0.

• Skips 12 characters, covering "First Line\n".

• The next character read is S from "Second Line".

• Line number updates to 1 because a newline (\n) was skipped.