Java: Convert InputStream to string

In this post, I am going to explain how to convert an InputStream to a String.

 

Approach 1: Read the stream character by character and append it to the StringBuilder.

public static String inputStreamToString1(InputStream inputStream, Charset charSet) throws IOException {
	StringBuilder stringBuilder = new StringBuilder();
	try (Reader reader = new BufferedReader(new InputStreamReader(inputStream, charSet))) {
		int c = 0;
		while ((c = reader.read()) != -1) {
			stringBuilder.append((char) c);
		}
	}

	return stringBuilder.toString();
}

 

Approach 2: Using BufferedReader lines() method.

public static String inputStreamToString2(InputStream inputStream, Charset charSet) throws IOException {

	try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, charSet))) {
		return reader.lines().collect(Collectors.joining("\n"));
	}

}

 

Approach 3: Using InputStream.readAllBytes() method.

 

'readAllBytes()' method is available from Java9, it returns a byte array containing the bytes read from this input stream.

public static String inputStreamToString3(InputStream inputStream, Charset charSet) throws IOException {
	return new String(inputStream.readAllBytes(), charSet);
}

Find the below working application.

 

App.java

package com.sample.app;

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

public class App {

	public static String inputStreamToString1(InputStream inputStream, Charset charSet) throws IOException {
		StringBuilder stringBuilder = new StringBuilder();
		try (Reader reader = new BufferedReader(new InputStreamReader(inputStream, charSet))) {
			int c = 0;
			while ((c = reader.read()) != -1) {
				stringBuilder.append((char) c);
			}
		}

		return stringBuilder.toString();
	}

	public static String inputStreamToString2(InputStream inputStream, Charset charSet) throws IOException {

		try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, charSet))) {
			return reader.lines().collect(Collectors.joining("\n"));
		}

	}

	public static String inputStreamToString3(InputStream inputStream, Charset charSet) throws IOException {
		return new String(inputStream.readAllBytes(), charSet);
	}

	public static void main(String[] args) throws IOException {
		InputStream inputStream1 = new ByteArrayInputStream("Hello World".getBytes());
		InputStream inputStream2 = new ByteArrayInputStream("Hello World".getBytes());
		InputStream inputStream3 = new ByteArrayInputStream("Hello World".getBytes());

		String str1 = inputStreamToString1(inputStream1, StandardCharsets.UTF_8);
		String str2 = inputStreamToString1(inputStream2, StandardCharsets.UTF_8);
		String str3 = inputStreamToString1(inputStream3, StandardCharsets.UTF_8);

		System.out.println(str1);
		System.out.println(str2);
		System.out.println(str3);
	}
}

Output

Hello World
Hello World
Hello World

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