StringUtils.java

/*
 * Copyright (C) 2009-2010, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.util;

import java.text.MessageFormat;
import java.util.Collection;

import org.eclipse.jgit.internal.JGitText;

/**
 * Miscellaneous string comparison utility methods.
 */
public final class StringUtils {
    private static final char[] LC;

    static {
        LC = new char['Z' + 1];
        for (char c = 0; c < LC.length; c++)
            LC[c] = c;
        for (char c = 'A'; c <= 'Z'; c++)
            LC[c] = (char) ('a' + (c - 'A'));
    }

    /**
     * Convert the input to lowercase.
     * <p>
     * This method does not honor the JVM locale, but instead always behaves as
     * though it is in the US-ASCII locale. Only characters in the range 'A'
     * through 'Z' are converted. All other characters are left as-is, even if
     * they otherwise would have a lowercase character equivalent.
     *
     * @param c
     *            the input character.
     * @return lowercase version of the input.
     */
    public static char toLowerCase(char c) {
        return c <= 'Z' ? LC[c] : c;
    }

    /**
     * Convert the input string to lower case, according to the "C" locale.
     * <p>
     * This method does not honor the JVM locale, but instead always behaves as
     * though it is in the US-ASCII locale. Only characters in the range 'A'
     * through 'Z' are converted, all other characters are left as-is, even if
     * they otherwise would have a lowercase character equivalent.
     *
     * @param in
     *            the input string. Must not be null.
     * @return a copy of the input string, after converting characters in the
     *         range 'A'..'Z' to 'a'..'z'.
     */
    public static String toLowerCase(String in) {
        final StringBuilder r = new StringBuilder(in.length());
        for (int i = 0; i < in.length(); i++)
            r.append(toLowerCase(in.charAt(i)));
        return r.toString();
    }


    /**
     * Borrowed from commons-lang <code>StringUtils.capitalize()</code> method.
     *
     * <p>
     * Capitalizes a String changing the first letter to title case as per
     * {@link java.lang.Character#toTitleCase(char)}. No other letters are
     * changed.
     * </p>
     * <p>
     * A <code>null</code> input String returns <code>null</code>.
     * </p>
     *
     * @param str
     *            the String to capitalize, may be null
     * @return the capitalized String, <code>null</code> if null String input
     * @since 4.0
     */
    public static String capitalize(String str) {
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return str;
        }
        return new StringBuilder(strLen)
                .append(Character.toTitleCase(str.charAt(0)))
                .append(str.substring(1)).toString();
    }

    /**
     * Test if two strings are equal, ignoring case.
     * <p>
     * This method does not honor the JVM locale, but instead always behaves as
     * though it is in the US-ASCII locale.
     *
     * @param a
     *            first string to compare.
     * @param b
     *            second string to compare.
     * @return true if a equals b
     */
    public static boolean equalsIgnoreCase(String a, String b) {
        if (References.isSameObject(a, b)) {
            return true;
        }
        if (a.length() != b.length())
            return false;
        for (int i = 0; i < a.length(); i++) {
            if (toLowerCase(a.charAt(i)) != toLowerCase(b.charAt(i)))
                return false;
        }
        return true;
    }

    /**
     * Compare two strings, ignoring case.
     * <p>
     * This method does not honor the JVM locale, but instead always behaves as
     * though it is in the US-ASCII locale.
     *
     * @param a
     *            first string to compare.
     * @param b
     *            second string to compare.
     * @since 2.0
     * @return an int.
     */
    public static int compareIgnoreCase(String a, String b) {
        for (int i = 0; i < a.length() && i < b.length(); i++) {
            int d = toLowerCase(a.charAt(i)) - toLowerCase(b.charAt(i));
            if (d != 0)
                return d;
        }
        return a.length() - b.length();
    }

    /**
     * Compare two strings, honoring case.
     * <p>
     * This method does not honor the JVM locale, but instead always behaves as
     * though it is in the US-ASCII locale.
     *
     * @param a
     *            first string to compare.
     * @param b
     *            second string to compare.
     * @since 2.0
     * @return an int.
     */
    public static int compareWithCase(String a, String b) {
        for (int i = 0; i < a.length() && i < b.length(); i++) {
            int d = a.charAt(i) - b.charAt(i);
            if (d != 0)
                return d;
        }
        return a.length() - b.length();
    }

    /**
     * Parse a string as a standard Git boolean value. See
     * {@link #toBooleanOrNull(String)}.
     *
     * @param stringValue
     *            the string to parse.
     * @return the boolean interpretation of {@code value}.
     * @throws java.lang.IllegalArgumentException
     *             if {@code value} is not recognized as one of the standard
     *             boolean names.
     */
    public static boolean toBoolean(String stringValue) {
        if (stringValue == null)
            throw new NullPointerException(JGitText.get().expectedBooleanStringValue);

        final Boolean bool = toBooleanOrNull(stringValue);
        if (bool == null)
            throw new IllegalArgumentException(MessageFormat.format(JGitText.get().notABoolean, stringValue));

        return bool.booleanValue();
    }

    /**
     * Parse a string as a standard Git boolean value.
     * <p>
     * The terms {@code yes}, {@code true}, {@code 1}, {@code on} can all be
     * used to mean {@code true}.
     * <p>
     * The terms {@code no}, {@code false}, {@code 0}, {@code off} can all be
     * used to mean {@code false}.
     * <p>
     * Comparisons ignore case, via {@link #equalsIgnoreCase(String, String)}.
     *
     * @param stringValue
     *            the string to parse.
     * @return the boolean interpretation of {@code value} or null in case the
     *         string does not represent a boolean value
     */
    public static Boolean toBooleanOrNull(String stringValue) {
        if (stringValue == null)
            return null;

        if (equalsIgnoreCase("yes", stringValue) //$NON-NLS-1$
                || equalsIgnoreCase("true", stringValue) //$NON-NLS-1$
                || equalsIgnoreCase("1", stringValue) //$NON-NLS-1$
                || equalsIgnoreCase("on", stringValue)) //$NON-NLS-1$
            return Boolean.TRUE;
        else if (equalsIgnoreCase("no", stringValue) //$NON-NLS-1$
                || equalsIgnoreCase("false", stringValue) //$NON-NLS-1$
                || equalsIgnoreCase("0", stringValue) //$NON-NLS-1$
                || equalsIgnoreCase("off", stringValue)) //$NON-NLS-1$
            return Boolean.FALSE;
        else
            return null;
    }

    /**
     * Join a collection of Strings together using the specified separator.
     *
     * @param parts
     *            Strings to join
     * @param separator
     *            used to join
     * @return a String with all the joined parts
     */
    public static String join(Collection<String> parts, String separator) {
        return StringUtils.join(parts, separator, separator);
    }

    /**
     * Join a collection of Strings together using the specified separator and a
     * lastSeparator which is used for joining the second last and the last
     * part.
     *
     * @param parts
     *            Strings to join
     * @param separator
     *            separator used to join all but the two last elements
     * @param lastSeparator
     *            separator to use for joining the last two elements
     * @return a String with all the joined parts
     */
    public static String join(Collection<String> parts, String separator,
            String lastSeparator) {
        StringBuilder sb = new StringBuilder();
        int i = 0;
        int lastIndex = parts.size() - 1;
        for (String part : parts) {
            sb.append(part);
            if (i == lastIndex - 1) {
                sb.append(lastSeparator);
            } else if (i != lastIndex) {
                sb.append(separator);
            }
            i++;
        }
        return sb.toString();
    }

    private StringUtils() {
        // Do not create instances
    }

    /**
     * Test if a string is empty or null.
     *
     * @param stringValue
     *            the string to check
     * @return <code>true</code> if the string is <code>null</code> or empty
     */
    public static boolean isEmptyOrNull(String stringValue) {
        return stringValue == null || stringValue.length() == 0;
    }

    /**
     * Replace CRLF, CR or LF with a single space.
     *
     * @param in
     *            A string with line breaks
     * @return in without line breaks
     * @since 3.1
     */
    public static String replaceLineBreaksWithSpace(String in) {
        char[] buf = new char[in.length()];
        int o = 0;
        for (int i = 0; i < buf.length; ++i) {
            char ch = in.charAt(i);
            switch (ch) {
            case '\r':
                if (i + 1 < buf.length && in.charAt(i + 1) == '\n') {
                    buf[o++] = ' ';
                    ++i;
                } else
                    buf[o++] = ' ';
                break;
            case '\n':
                buf[o++] = ' ';
                break;
            default:
                buf[o++] = ch;
                break;
            }
        }
        return new String(buf, 0, o);
    }
}