Java File Read by Charset bomStream(String charset, String file)

Description

Convert stream to ByteArrayInputStream by given character set.

License

Open Source License

Parameter

Parameter	Description
charset	target character set.
file	a file that contains no BOM head content.

Exception

Parameter	Description
IOException	I/O operation failed or unsupported character set.

Return

a ByteArrayInputStream contains BOM heads and bytes in original stream

Declaration

public static InputStream bomStream(String charset, String file) throws IOException 

Method Source Code

//package com.java2s;
/*//from   ww w. j av  a  2s  .c o  m
 * Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.io.ByteArrayInputStream;

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

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

import java.nio.charset.UnsupportedCharsetException;
import java.nio.file.Files;
import java.nio.file.Paths;

import java.util.HashMap;

import java.util.Map;

import java.util.stream.Collectors;

public class Main {
    /**
     * BOM table for storing BOM header.
     */
    private final static Map<String, byte[]> bom = new HashMap();

    /**
     * Convert stream to ByteArrayInputStream by given character set.
     * @param charset target character set.
     * @param file a file that contains no BOM head content.
     * @return a ByteArrayInputStream contains BOM heads and bytes in original
     *         stream
     * @throws IOException I/O operation failed or unsupported character set.
     */
    public static InputStream bomStream(String charset, String file) throws IOException {
        String localCharset = charset;
        if (charset.equals("UTF-16") || charset.equals("UTF-32")) {
            localCharset += ByteOrder.nativeOrder() == ByteOrder.BIG_ENDIAN ? "BE" : "LE";
        }
        if (!bom.containsKey(localCharset))
            throw new UnsupportedCharsetException("Charset:" + localCharset);

        byte[] content = Files.readAllLines(Paths.get(file)).stream().collect(Collectors.joining())
                .getBytes(localCharset);
        byte[] head = bom.get(localCharset);
        ByteBuffer bb = ByteBuffer.allocate(content.length + head.length);
        bb.put(head);
        bb.put(content);
        return new ByteArrayInputStream(bb.array());
    }
}

Related

1. copyFileWithEolConversion(File inFile, File outFile, Charset charset)
2. detectCharset(File f, String[] charsets)
3. doTranseFileCharset(File srcFile, File destFile, String srcCharsetName, String destCharsetName)
4. fileContent(File file, Charset charset)