Convert OutputStream to String in Java

‘java.io.OutputStream’  is the abstract superclass of all the classes representing an output stream of bytes. An output stream accepts output bytes and sends them to some sink/destination.

 

Following examples explain how to convert different a ByteArrayOutputStream object to string in Java.

 

Example 1: Convert ByteArrayOutputStream to string.

 

Get the byte array from ByteArrayOutputStream object.

byte[] byteArr = byteArrayOutputStream.toByteArray();

Initialize the string using byte array.

String str2 = new String(byteArr);

Find the below working application.

 

OutputStreamToStringDemo1.java

package com.sample.app.streams;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class OutputStreamToStringDemo1 {

	public static void main(String[] args) throws IOException {
		try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {
			String str1 = "Hello World!!!!";
			byteArrayOutputStream.write(str1.getBytes());

			byte[] byteArr = byteArrayOutputStream.toByteArray();
			String str2 = new String(byteArr);

			System.out.println("str1 : " + str1);
			System.out.println("str2 : " + str2);
		}

	}

}

Output

str1 : Hello World!!!!
str2 : Hello World!!!!

Example 2: Using toString method of ByteArrayOutputStream.

ByteArrayOutputString#toString method converts the buffer's contents into a string decoding bytes using the platform's default character set.

String str2 = byteArrayOutputStream.toString();

OutputStreamToStringDemo2.java

package com.sample.app.streams;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class OutputStreamToStringDemo2 {

	public static void main(String[] args) throws IOException {
		try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {
			String str1 = "Hello World!!!!";
			byteArrayOutputStream.write(str1.getBytes());

			String str2 = byteArrayOutputStream.toString();

			System.out.println("str1 : " + str1);
			System.out.println("str2 : " + str2);
		}

	}

}

Output

str1 : Hello World!!!!
str2 : Hello World!!!!

You can even set the character set to decode the byte array to string using following toString methods.

public synchronized String toString(Charset charset)

public synchronized String toString(String charsetName)

Converts the buffer's contents into a string by decoding the bytes using the specified charset.

 

An invocation of this method of the form

String str = byteArrayOutputStream.toString("UTF-8");

 

behaves in exactly the same way as the below expression.

String str = byteArrayOutputStream.toString(StandardCharsets.UTF_8);

 

OutputStreamToStringDemo3.java

package com.sample.app.streams;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

public class OutputStreamToStringDemo3 {

	public static void main(String[] args) throws IOException {
		try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {
			String str1 = "Hello World!!!!";
			byteArrayOutputStream.write(str1.getBytes());

			String str2 = byteArrayOutputStream.toString("UTF-8");
			String str3 = byteArrayOutputStream.toString(StandardCharsets.UTF_8);

			System.out.println("str1 : " + str1);
			System.out.println("str2 : " + str2);
			System.out.println("str3 : " + str3);
		}

	}

}

Output

str1 : Hello World!!!!
str2 : Hello World!!!!
str3 : Hello World!!!!

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Implement ByteBuffer input stream

Channels and Buffers are the basic building blocks of Java NIO. Channels are analogous to the streams in IO. All the data should go via channels. If you send any data to channel, the data is placed in a buffer. Any data that is read from a channel is read into a buffer. Buffer is a container that holds some data.

 

Let’s create ByteBufferInputStream by extending InputStream class.

 

ByteBufferInputStream.java

package com.sample.app.streams;

import static java.lang.Math.max;
import static java.lang.Math.min;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;

public class ByteBufferInputStream extends InputStream {

	private final ByteBuffer byteBuffer;

	public ByteBufferInputStream(final ByteBuffer byteBuffer) {
		this.byteBuffer = byteBuffer.slice();
	}

	@Override
	public int read() {
		// a & 0xff will give the lowest 8 bits from a. If a is less than 255, it'll
		// return the same number.
		if (byteBuffer.hasRemaining()) {
			return 0xff & byteBuffer.get();
		}

		return -1;
	}

	@Override
	public int read(final byte b[], final int off, final int len) {
		final int minLength = min(len, byteBuffer.remaining());
		byteBuffer.get(b, off, minLength);
		return minLength;
	}

	@Override
	public long skip(long noOfLinesToSkip) {
		final long minLinesToSlip = min(byteBuffer.remaining(), max(noOfLinesToSkip, 0));
		byteBuffer.position((int) (byteBuffer.position() + minLinesToSlip));
		return minLinesToSlip;
	}

	@Override
	public synchronized int available() {
		return byteBuffer.remaining();
	}

	@Override
	public void close() throws IOException {
		// not applicable
	}
}

 

App.java

package com.sample.app;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;

import com.sample.app.streams.ByteBufferInputStream;

public class App {

	public static void main(String[] args) throws IOException {
		ByteBuffer byteBuffer = ByteBuffer.allocate(100);
		byteBuffer.put("one\n".getBytes(StandardCharsets.UTF_8));
		byteBuffer.put("two\n".getBytes(StandardCharsets.UTF_8));
		byteBuffer.put("three\n".getBytes(StandardCharsets.UTF_8));
		byteBuffer.put("four\n".getBytes(StandardCharsets.UTF_8));
		byteBuffer.put("five\n".getBytes(StandardCharsets.UTF_8));

		byteBuffer.flip();

		try (ByteBufferInputStream byteBufferInputStream = new ByteBufferInputStream(byteBuffer)) {
			StringBuilder stringBuilder = new StringBuilder();

			int data;
			while ((data = byteBufferInputStream.read()) != -1) {
				stringBuilder.append((char) data);
			}

			System.out.println(stringBuilder.toString());
		}

	}

}

 

Output

one
two
three
four
five

 

 

 

 

  

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File programs in Java

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      Compress and archive files in zip format

      Decompress files from zip file

      File utilities application using Guava package

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      Encrypt and decrypt XML file in Java

      Create Password Protected zip file in Java

      Place a file in project class path

      Accessing meta data of a file (All attributes of file)

      Set Unique Identifier to File in Java

      Set File permissions in Java

      File Tail implementation in Java

      Launch URI Scheme over java file

      DigestInputStream & DigestOutputStream Example

      Move file to recycle bin

      Generate content hash of a file

      HOW TO GENERATE SHA1 HASH VALUE OF FILE

      HOW TO GENERATE MD5 HASH VALUE OF FILE

      List contents of a zip file

      Split file path using system file separator symbol

      Split the string using file Path separator

      File.separator vs File.pathSeparator

      Encrypt and Decrypt file/stream in Java

      Print all the file names recursively

      How to write multiple input streams to a file

      Working with RandomAccessFile in Java

      Java write to a file using BufferedWriter

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       Java: Programmatically import certificate to cacerts file

      Apache commons io: Download a file from url

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      Redirect System.out.println statements to a stream or file

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      Append text to a file

      Create and write text content to a file

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      Search for files in a folder

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      Open a file

      Convert InputStream to ByteArray

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      Read file content as string

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      Sort the files by their last modified date

      Sort files by their name

      Sort files by their size

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Lucene: How to get TokenStream?

TokenStream represents an intermediate data format between different components of analysis process and it is an enumeration of tokens. Analyzer can take a Reader as input and output TokenStream.

 

Example

Analyzer analyzer = new EnglishAnalyzer();
Reader reader = new StringReader("Text to be passed");
TokenStream tokenStream = analyzer.tokenStream("myField", reader);

 

App.java

package com.sample.app;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.en.EnglishAnalyzer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;

public class App {

	public static void main(String args[]) throws IOException {

		try (Analyzer analyzer = new EnglishAnalyzer()) {
			Reader reader = new StringReader("Java is a Programming Language");
			TokenStream tokenStream = analyzer.tokenStream("myField", reader);

			CharTermAttribute charTermAttribute = tokenStream.addAttribute(CharTermAttribute.class);

			tokenStream.reset();

			while (tokenStream.incrementToken()) {
				System.out.println(charTermAttribute.toString());
			}
		}

	}

}

 

Output

java
program
languag

 

  

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Ignore duplicates while producing map from a stream

Using merge function, we can specify how to resolve collisions associated with same key.

Example

Map<String, String> map = emps.stream()

.collect(Collectors.toMap(Employee::getFirstName, Employee::getLastName, (value1, value2) -> {

         return value1;

}));

Above snippet specifies in case of collisions take first value.

Employee.java

package com.sample.app.model;

public class Employee {
 private String firstName;
 private String lastName;

 public Employee(String firstName, String lastName) {
  super();
  this.firstName = firstName;
  this.lastName = lastName;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 @Override
 public int hashCode() {
  final int prime = 31;
  int result = 1;
  result = prime * result + ((firstName == null) ? 0 : firstName.hashCode());
  result = prime * result + ((lastName == null) ? 0 : lastName.hashCode());
  return result;
 }

 @Override
 public boolean equals(Object obj) {
  if (this == obj)
   return true;
  if (obj == null)
   return false;
  if (getClass() != obj.getClass())
   return false;
  Employee other = (Employee) obj;
  if (firstName == null) {
   if (other.firstName != null)
    return false;
  } else if (!firstName.equals(other.firstName))
   return false;
  if (lastName == null) {
   if (other.lastName != null)
    return false;
  } else if (!lastName.equals(other.lastName))
   return false;
  return true;
 }

}

App.java

package com.sample.app;

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import com.sample.app.model.Employee;

public class App {

 public static void main(String args[]) throws InterruptedException {
  Employee emp1 = new Employee("Ram", "Gurram");
  Employee emp2 = new Employee("Siva", "Ponnam");
  Employee emp3 = new Employee("Sailaja", "Navakotla");
  Employee emp4 = new Employee("Ram", "Battu");

  List<Employee> emps = Arrays.asList(emp1, emp2, emp3, emp4);

  Map<String, String> map = emps.stream()
    .collect(Collectors.toMap(Employee::getFirstName, Employee::getLastName, (value1, value2) -> {
     return value1;
    }));

  for (String firstName : map.keySet()) {
   System.out.println(firstName + " , " + map.get(firstName));
  }
 }

}

Output

Sailaja , Navakotla

Siva , Ponnam

Ram , Gurram

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