How to Convert String to InputStream

1. Introduction

In this tutorial we are going to look at how to convert String to InputStream in Java. We will present solutions in plain Java and will use external libraries like Guava and Apache Commons IO.

For more Java I/O related articles, check the following links:

• Java I/O Tutorials,
• More convert-related articles,
• InputStream to String.

2. Convert String to InputStream using ByteArrayInputStream

The solution in plain Java is almost straightforward and, which is also important, we can achieve a wanted result without additional dependencies.

The following example shows how to use ByteArrayInputStream to convert String to InputStream:

package com.frontbackend.java.io.conversions.string.toinputstream;

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

public class StringToInputStreamUsingByteArrayInputStream {

    public static void main(String[] args) {
        String str = "frontbackend.com";

        InputStream result = new ByteArrayInputStream(str.getBytes(StandardCharsets.UTF_8));
    }
}

In this example first, we get bytes representing the String encoded using UTF-8 charset. Then, we create ByteArrayInputStream instance that takes byte array as a constructor parameter.

Note that we should always provide the encoding of the given string unless the encoding matches the default platform charset.

3. Using Guava to convert String to InputStream

With Guava we can also achieve conversions from String to InputStream, however, the solution is more complex:

package com.frontbackend.java.io.conversions.string.toinputstream;

import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.io.input.ReaderInputStream;

import com.google.common.base.Charsets;
import com.google.common.io.CharSource;

public class StringToInputStreamUsingGuava {

    public static void main(String[] args) throws IOException {
        String str = "frontbackend.com";

        InputStream result = new ReaderInputStream(CharSource.wrap(str)
                                                             .openStream(),
                Charsets.UTF_8);
    }
}

First, we are creating Reader object using CharSource.wrap(str).openStream() method. Then, we used ReaderInputStream to convert Reader to the InputStream.

Note that using ReaderInputStream constructor without a charset as a second parameter (charset) is deprecated now.

4. Converting String to InputStream using IOUtils from Apache Commons IO

Using IOUtils class from Apache Commons IO gives us a pretty straightforward solution:

package com.frontbackend.java.io.conversions.string.toinputstream;

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

import org.apache.commons.io.IOUtils;

public class StringToInputStreamUsingIOUtils {

    public static void main(String[] args) throws IOException {
        String str = "frontbackend.com";

        InputStream stream = IOUtils.toInputStream(str, StandardCharsets.UTF_8);
    }
}

Here we have dedicated method IOUtils.toInputStream that do the conversion transparently.

Note that using IOUtils.toInputStream(str) with a single parameter is deprecated. Now we need to explicitly specify the encoding of the String as a second parameter.

5. Conclusion

In this article, we illustrated several methods to convert String to InputStream in Java. The important knowledge to remember is when we convert String to the byte stream we should always provide the encoding.

If you are looking for reverse method, that converts InputStream to a String check the following: InputStream -> String

As usual, code use in this article is available under our GitHub repository.