Convert Java InputStream to String

By admin | December 13, 2017 | Updated : February 12, 2018 java, No Comments

In this tutorial, I am showing how to convert Java InputStream to String using Plain Java, Java 8, Apache Commons IO library and Guava.

An InputStream is connected to some data streams like a file, memory bufferes, network connection, pipe etc. It is used for reading the data from above sources.

You can also see an example for convert Java String to InputStream (java String to InputStream).

Convert InputStream to String Using JDK

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;



public class Test {

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

                String hello = "hello world";
                InputStream is = new ByteArrayInputStream( hello.getBytes(StandardCharsets.UTF_8) );
                Scanner s = new Scanner(is).useDelimiter("\\A");
                String result = s.hasNext() ? s.next() : "";
                System.out.println(result);

        }
}

In below example, we are using InputStreamReader for converting InputStream to string

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.nio.charset.StandardCharsets;

public class Test {

        public static void main(String[] args) throws IOException {
                String hello = "hello world";
                InputStream is = new ByteArrayInputStream(hello.getBytes(StandardCharsets.UTF_8));
                final int buffSize = 1024;
                final char[] buff = new char[buffSize];
                final StringBuilder result = new StringBuilder();
                Reader in = new InputStreamReader(is, "UTF-8");
                int read;
                while ((read = in.read(buff, 0, buff.length)) != -1) {
                        result.append(buff, 0, read);
                }
                System.out.println(result);

        }
}

In below example, we are using ByteArrayOutputStream for converting InputStream to string

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

public class Test {

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

                String hello = "hello world";
                InputStream is = new ByteArrayInputStream(hello.getBytes(StandardCharsets.UTF_8));
                ByteArrayOutputStream buffer = new ByteArrayOutputStream();
                int read;
                byte[] buff = new byte[1024];
                while ((read = is.read(buff, 0, buff.length)) != -1) {
                        buffer.write(buff, 0, read);
                }
                buffer.flush();
                byte[] byteArray = buffer.toByteArray();
                String result = new String(byteArray, StandardCharsets.UTF_8);
                System.out.println(result);

        }
}

Convert InputStream to String Using Java 8

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.stream.Collectors;

public class Test {

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

                String hello = "hello world";
                InputStream is = new ByteArrayInputStream(hello.getBytes(StandardCharsets.UTF_8));
                String result = new BufferedReader(new InputStreamReader(is)).lines().collect(Collectors.joining("\n"));
                System.out.println(result);

        }
}

Convert InputStream to String Using Apache Commons IOUtils

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import org.apache.commons.io.IOUtils;

public class Test {

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

                String hello = "hello world";
                InputStream is = new ByteArrayInputStream(hello.getBytes(StandardCharsets.UTF_8));
                String result = IOUtils.toString(is, StandardCharsets.UTF_8);
                System.out.println(result);

        }
}

In below example, you can also use IOUtils.copy of IOUtils to convert InputStream to String.

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringWriter;
import java.nio.charset.StandardCharsets;
import org.apache.commons.io.IOUtils;

public class Test {

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

                String hello = "hello world";
                InputStream is = new ByteArrayInputStream(hello.getBytes(StandardCharsets.UTF_8));
                StringWriter result = new StringWriter();
                IOUtils.copy(is, result, "UTF-8");
                System.out.println(result);

        }
}

Convert InputStream to String Using Guava

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import com.google.common.base.Charsets;
import com.google.common.io.CharStreams;

public class Test {

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

                String hello = "hello world";
                InputStream is = new ByteArrayInputStream(hello.getBytes(StandardCharsets.UTF_8));
                String result = CharStreams.toString(new InputStreamReader(
                              is, Charsets.UTF_8));
                System.out.println(result);

        }
}

Output

hello world