Java URI from toURI(final java.io.File file, final StringBuilder builder)

Description

A method to return a file URI from a file, without creating lots of char[] garbage.

License

Open Source License

Parameter

Parameter	Description
file	The file to get a URI for.
builder	A StringBuilder to help build the URI path.

Return

A URI for the file.

Declaration

public static URI toURI(final java.io.File file,
        final StringBuilder builder) 

Method Source Code

//package com.java2s;
import java.net.URI;
import java.net.URISyntaxException;

public class Main {
    private static final char FORWARD_SLASH = '/';

    /**/*  w ww  .  j av  a 2  s  .c  om*/
     * A method to return a file URI from a file, without creating lots of char[] garbage.
     * <p>
     * The method in File.toURI() creates a lot of char[] garbage as it appends slashes
     * and doesn't use a single stringbuilder.  This method also allows us to pass in
     * an external string builder, so we can re-use an existing one.
     *
     * @param file  The file to get a URI for.
     * @param builder A StringBuilder to help build the URI path.
     * @return A URI for the file.
     */
    //CHECKSTYLE:OFF  Too complex
    public static URI toURI(final java.io.File file,
            final StringBuilder builder) {

        java.io.File absoluteFile = file.getAbsoluteFile();

        //Allow for Mockito tests where the previous assignment returns a null reference
        if (absoluteFile == null) {
            absoluteFile = new java.io.File(file.getAbsolutePath());
        }

        final String path = absoluteFile.getPath();
        final int length = path.length();
        final char separator = java.io.File.separatorChar;

        // check how many start slashes we need.
        int numStartSlashes = 0;
        if (path.charAt(0) != separator) {
            numStartSlashes = 1;
        } else if (path.charAt(1) == separator) {
            numStartSlashes = 2;
        }

        // reset the builder to the start:
        builder.setLength(0);

        // do URI forward slashes
        for (int startSlashNum = 0; startSlashNum < numStartSlashes; startSlashNum++) {
            builder.append(FORWARD_SLASH);
        }

        // append path (transforming separators to forward slashes if necessary):
        if (separator == FORWARD_SLASH) {
            builder.append(path);
        } else {
            for (int charIndex = 0; charIndex < length; charIndex++) {
                final char theChar = path.charAt(charIndex);
                if (theChar == separator) {
                    builder.append(FORWARD_SLASH);
                } else {
                    builder.append(theChar);
                }
            }
        }

        // ensure we have a closing slash if the file is a directory:
        if (path.charAt(path.length() - 1) != separator
                && absoluteFile.isDirectory()) {
            builder.append(FORWARD_SLASH);
        }

        URI uri = null;
        try {
            uri = new URI("file", null, builder.toString(), null);
        } catch (URISyntaxException e) {
            // ignore - should never happen.
        }
        //CHECKSTYLE:ON
        return uri;
    }
}

Related

1. toURI(CharSequence uriStr)
2. toURI(File f)
3. toUri(File folder)
4. toURI(final String location)
5. toURI(final String path)
6. toURI(final String uriString)
7. toUri(java.io.File file)