Java Javascript String Unescape unescapeJavaString(String str)

Description

Unescapes any Java literals found in the String.

For example, it will turn a sequence of '\' and 'n' into a newline character, unless the '\' is preceded by another '\'.

A null string input has no effect.

License

Apache License

Parameter

Parameter	Description
str	the <code>String</code> to unescape, may be null

Exception

Parameter	Description
IllegalArgumentException	if invalid unicode arguments

Declaration

public static String unescapeJavaString(String str)

Method Source Code

//package com.java2s;
/*//w w w .j ava  2 s  . com
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License. 
 */

public class Main {
    /**
     * <p>Unescapes any Java literals found in the <code>String</code>.</p>
     *
     * <p>For example, it will turn a sequence of <code>'\'</code> and
     * <code>'n'</code> into a newline character, unless the <code>'\'</code>
     * is preceded by another <code>'\'</code>.</p>
     * 
     * <p>A <code>null</code> string input has no effect.</p>
     * 
     * @param str  the <code>String</code> to unescape, may be null
     * @returns unescaped string
     * @throws IllegalArgumentException if invalid unicode arguments
     */
    public static String unescapeJavaString(String str) {

        if (str == null) {
            return null;
        }

        StringBuffer out = new StringBuffer();
        int sz = str.length();
        StringBuffer unicode = new StringBuffer(4);
        boolean hadSlash = false;
        boolean inUnicode = false;
        for (int i = 0; i < sz; i++) {
            char ch = str.charAt(i);
            if (inUnicode) {
                // if in unicode, then we're reading unicode
                // values in somehow
                unicode.append(ch);
                if (unicode.length() == 4) {
                    // unicode now contains the four hex digits
                    // which represents our unicode character
                    try {
                        int value = Integer.parseInt(unicode.toString(), 16);
                        out.append((char) value);
                        unicode.setLength(0);
                        inUnicode = false;
                        hadSlash = false;
                    } catch (NumberFormatException nfe) {
                        throw new IllegalArgumentException("Unable to parse unicode value: " + unicode, nfe);
                    }
                }
                continue;
            }
            if (hadSlash) {
                // handle an escaped value
                hadSlash = false;
                switch (ch) {
                case '\\':
                    out.append('\\');
                    break;
                case '\'':
                    out.append('\'');
                    break;
                case '\"':
                    out.append('"');
                    break;
                case 'r':
                    out.append('\r');
                    break;
                case 'f':
                    out.append('\f');
                    break;
                case 't':
                    out.append('\t');
                    break;
                case 'n':
                    out.append('\n');
                    break;
                case 'b':
                    out.append('\b');
                    break;
                case 'u': {
                    // uh-oh, we're in unicode country....
                    inUnicode = true;
                    break;
                }
                default:
                    out.append(ch);
                    break;
                }
                continue;
            } else if (ch == '\\') {
                hadSlash = true;
                continue;
            }
            out.append(ch);
        }
        if (hadSlash) {
            // then we're in the weird case of a \ at the end of the
            // string, let's output it anyway.
            out.append('\\');
        }
        return out.toString();
    }
}