Java OutputStream – How to Write Strings

javaoutputstreamstring

How can I create class that takes an implentation of OutputStream and writes the the content to it?

For example, the following print method is wrong and will not compile. What are the options or better techniques?

public class FooBarPrinter{
    private OutputStream o;
    public FooBarPrinter(OutputStream o){
        this.o=o;
    }

    public void print(String s){        
        o.write(s);
    }
}

Best Answer

A generic OutputStream doesn't have the ability to write a String directly to it. Instead, you need to get the byte[] of the String and then write them out to the stream.

public void print(String s){ 
    o.write(s.getBytes());
}

Refer to the OutputStream java documentation for more information on the supported write data types.

My suggestion for making this better is to make sure the OutputStream you provide in the constructor is a BufferedOutputStream, as this will improve the performance of your code. It works by buffering some of the data in memory, and writing it out to disk in big chunks instead of many smaller writes.

Here is the java documentation for BufferedOutputStream

Related Solutions

Java – How to Write String to Output Stream

Streams (InputStream and OutputStream) transfer binary data. If you want to write a string to a stream, you must first convert it to bytes, or in other words encode it. You can do that manually (as you suggest) using the String.getBytes(Charset) method, but you should avoid the String.getBytes() method, because that uses the default encoding of the JVM, which can't be reliably predicted in a portable way.

The usual way to write character data to a stream, though, is to wrap the stream in a Writer, (often a PrintWriter), that does the conversion for you when you call its write(String) (or print(String)) method. The corresponding wrapper for InputStreams is a Reader.

PrintStream is a special OutputStream implementation in the sense that it also contain methods that automatically encode strings (it uses a writer internally). But it is still a stream. You can safely wrap your stream with a writer no matter if it is a PrintStream or some other stream implementation. There is no danger of double encoding.

Example of PrintWriter with OutputStream:

try (PrintWriter p = new PrintWriter(new FileOutputStream("output-text.txt", true))) {
    p.println("Hello");
} catch (FileNotFoundException e1) {
    e1.printStackTrace();
}

Best Answer

Related Solutions

Java – How to Write String to Output Stream

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