Java String Whitespace Collapse collapseWhitespace(String str)

Description

collapse Whitespace

License

Open Source License

Declaration

public static String collapseWhitespace(String str) 

Method Source Code

//package com.java2s;
/*//from w  ww .j a  v  a  2  s.  co m
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public class Main {
    public static String collapseWhitespace(String str) {
        if (!needsCollapsing(str)) {
            return str;
        }

        // the assumption is that most strings will not need to be collapsed,
        // so the code below will usually not be reached

        int len = str.length();
        char[] buf = new char[len];
        str.getChars(0, len, buf, 0);

        int leadingWSLen = 0;
        int trailingWSLen = 0;
        int spanLen = 0;

        for (int idx = 0; idx < len; ++idx) {
            if (Character.isWhitespace(buf[idx])) {
                ++spanLen;
            } else if (spanLen > 0) {
                if (spanLen == idx) {
                    // leading whitespace
                    leadingWSLen = spanLen;
                } else {
                    // non-leading, non-trailing whitespace

                    // ensure that the first whitespace character is a space
                    int firstWSIdx = idx - spanLen;
                    buf[firstWSIdx] = ' ';

                    if (spanLen > 1) {
                        // remove all but the first whitespace character
                        System.arraycopy(buf, idx, buf, firstWSIdx + 1, len - idx);
                        len -= (spanLen - 1);
                        idx = firstWSIdx + 1;
                    }
                }

                spanLen = 0;
            }
        }

        if (spanLen > 0) {
            // trailing whitespace
            trailingWSLen = spanLen;
        }

        return new String(buf, leadingWSLen, len - leadingWSLen - trailingWSLen);
    }

    public static boolean needsCollapsing(String str) {
        int len = str.length();
        int spanLen = 0;

        for (int idx = 0; idx < len; ++idx) {
            if (Character.isWhitespace(str.charAt(idx))) {
                ++spanLen;
            } else if (spanLen > 0) {
                if (spanLen == idx) {
                    // leading whitespace
                    return true;
                } else {
                    // non-leading, non-trailing whitespace
                    if (str.charAt(idx - spanLen) != ' ') {
                        // first whitespace character is not a space
                        return true;
                    }
                    if (spanLen > 1) {
                        // there is a span of multiple whitespace characters
                        return true;
                    }
                }

                spanLen = 0;
            }
        }

        if (spanLen > 0) {
            // trailing whitespace
            return true;
        }

        return false;
    }
}

Related

1. collapseWhiteSpace(final String s)
2. collapseWhiteSpace(String content)
3. collapseWhitespace(String in, char replacementChar)
4. collapseWhitespace(String s)
5. collapseWhitespace(String s, boolean trim)
6. collapseWhitespace(String string)
7. collapseWhiteSpace(String string)
8. collapseWhiteSpace(String text)
9. collapseWhitespace(String text)