Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;

import java.util.Collection;

public class Main {
    /**
     * The extension separator character.
     * @since 1.4
     */
    public static final char EXTENSION_SEPARATOR = '.';
    /**
     * The Unix separator character.
     */
    private static final char UNIX_SEPARATOR = '/';
    /**
     * The Windows separator character.
     */
    private static final char WINDOWS_SEPARATOR = '\\';

    /**
     * Checks whether the extension of the filename is that specified.
     * <p>
     * This method obtains the extension as the textual part of the filename
     * after the last dot. There must be no directory separator after the dot.
     * The extension check is case-sensitive on all platforms.
     *
     * @param filename  the filename to query, null returns false
     * @param extension  the extension to check for, null or empty checks for no extension
     * @return true if the filename has the specified extension
     */
    public static boolean isExtension(String filename, String extension) {
        if (filename == null) {
            return false;
        }
        if (extension == null || extension.length() == 0) {
            return indexOfExtension(filename) == -1;
        }
        String fileExt = getExtension(filename);
        return fileExt.equals(extension);
    }

    /**
     * Checks whether the extension of the filename is one of those specified.
     * <p>
     * This method obtains the extension as the textual part of the filename
     * after the last dot. There must be no directory separator after the dot.
     * The extension check is case-sensitive on all platforms.
     *
     * @param filename  the filename to query, null returns false
     * @param extensions  the extensions to check for, null checks for no extension
     * @return true if the filename is one of the extensions
     */
    public static boolean isExtension(String filename, String[] extensions) {
        if (filename == null) {
            return false;
        }
        if (extensions == null || extensions.length == 0) {
            return indexOfExtension(filename) == -1;
        }
        String fileExt = getExtension(filename);
        for (String extension : extensions) {
            if (fileExt.equals(extension)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Checks whether the extension of the filename is one of those specified.
     * <p>
     * This method obtains the extension as the textual part of the filename
     * after the last dot. There must be no directory separator after the dot.
     * The extension check is case-sensitive on all platforms.
     *
     * @param filename  the filename to query, null returns false
     * @param extensions  the extensions to check for, null checks for no extension
     * @return true if the filename is one of the extensions
     */
    public static boolean isExtension(String filename, Collection<String> extensions) {
        if (filename == null) {
            return false;
        }
        if (extensions == null || extensions.isEmpty()) {
            return indexOfExtension(filename) == -1;
        }
        String fileExt = getExtension(filename);
        for (String extension : extensions) {
            if (fileExt.equals(extension)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns the index of the last extension separator character, which is a dot.
     * <p>
     * This method also checks that there is no directory separator after the last dot.
     * To do this it uses {@link #indexOfLastSeparator(String)} which will
     * handle a file in either Unix or Windows format.
     * <p>
     * The output will be the same irrespective of the machine that the code is running on.
     *
     * @param filename  the filename to find the last path separator in, null returns -1
     * @return the index of the last separator character, or -1 if there
     * is no such character
     */
    public static int indexOfExtension(String filename) {
        if (filename == null) {
            return -1;
        }
        int extensionPos = filename.lastIndexOf(EXTENSION_SEPARATOR);
        int lastSeparator = indexOfLastSeparator(filename);
        return lastSeparator > extensionPos ? -1 : extensionPos;
    }

    /**
     * Gets the extension of a filename.
     * <p>
     * This method returns the textual part of the filename after the last dot.
     * There must be no directory separator after the dot.
     * <pre>
     * foo.txt      --> "txt"
     * a/b/c.jpg    --> "jpg"
     * a/b.txt/c    --> ""
     * a/b/c        --> ""
     * </pre>
     * <p>
     * The output will be the same irrespective of the machine that the code is running on.
     *
     * @param filename the filename to retrieve the extension of.
     * @return the extension of the file or an empty string if none exists or {@code null}
     * if the filename is {@code null}.
     */
    public static String getExtension(String filename) {
        if (filename == null) {
            return null;
        }
        int index = indexOfExtension(filename);
        if (index == -1) {
            return "";
        } else {
            return filename.substring(index + 1);
        }
    }

    /**
     * Returns the index of the last directory separator character.
     * <p>
     * This method will handle a file in either Unix or Windows format.
     * The position of the last forward or backslash is returned.
     * <p>
     * The output will be the same irrespective of the machine that the code is running on.
     *
     * @param filename  the filename to find the last path separator in, null returns -1
     * @return the index of the last separator character, or -1 if there
     * is no such character
     */
    public static int indexOfLastSeparator(String filename) {
        if (filename == null) {
            return -1;
        }
        int lastUnixPos = filename.lastIndexOf(UNIX_SEPARATOR);
        int lastWindowsPos = filename.lastIndexOf(WINDOWS_SEPARATOR);
        return Math.max(lastUnixPos, lastWindowsPos);
    }
}