Returns an ArrayList of strings, one for each line in the string after it has been wrapped to fit lines of maxWidth. This code assumes str is not null.

Description

Demo Code

//package com.java2s;
import java.awt.FontMetrics;
import java.util.*;

public class Main {
    /**//from  w w  w .j a  va  2 s  .  c  om
     * Returns an ArrayList of strings, one for each line in the string after it has
     * been wrapped to fit lines of <var>maxWidth</var>.<br><br>
     * This code assumes <var>str</var> is not <code>null</code>.
     * @param str The string to split
     * @param fm FontMetrics for calculations of string width
     * @param maxWidth The max line width in points
     * @return a non-empty list of strings
     */
    public static List<String> wrap(String str, FontMetrics fm, int maxWidth) {
        List<String> lines = splitIntoLines(str);
        if (lines.size() == 0)
            return lines;

        ArrayList<String> strings = new ArrayList<String>();
        Iterator<String> iter = lines.iterator();
        while (iter.hasNext())
            wrapLineInto((String) iter.next(), strings, fm, maxWidth);
        return strings;
    }

    /**
     * Returns an ArrayList of strings, one for each line in the string.<br><br>
     * This code assumes <var>str</var> is not <code>null</code>.
     * @param str The string to split
     * @return A non-empty list of strings
     */
    public static List<String> splitIntoLines(String str) {
        ArrayList<String> strings = new ArrayList<String>();

        int len = str.length();
        if (len == 0) {
            strings.add("");
            return strings;
        }

        int lineStart = 0;

        for (int i = 0; i < len; ++i) {
            char c = str.charAt(i);
            if (c == '\r') {
                int newlineLength = 1;
                if ((i + 1) < len && str.charAt(i + 1) == '\n')
                    newlineLength = 2;
                strings.add(str.substring(lineStart, i));
                lineStart = i + newlineLength;
                if (newlineLength == 2) // skip \n next time through loop
                    ++i;
            } else if (c == '\n') {
                strings.add(str.substring(lineStart, i));
                lineStart = i + 1;
            }
        }
        if (lineStart < len)
            strings.add(str.substring(lineStart));

        return strings;
    }

    /**
     * Wraps the line of text and add the new line(s) to <var>list</var>.
     * @param line A line of text to be wrapped
     * @param list The list of the wrapped lines
     * @param fm FontMetrics to measure the width of the strings
     * @param maxWidth Maximum width of the line(s)
     */
    public static void wrapLineInto(String line, List<String> list,
            FontMetrics fm, int maxWidth) {
        int len = line.length();
        int width;
        while (len > 0 && (width = fm.stringWidth(line)) > maxWidth) {
            // Guess where to split the line.
            int guess = len * maxWidth / width;
            // Try to split it at a space character between words.
            String before = line.substring(0, guess).trim();

            width = fm.stringWidth(before);
            int pos;
            if (width > maxWidth) // The line is too long
                pos = findBreakBefore(line, guess);
            else { // The line is either too short or the required length
                pos = findBreakAfter(line, guess);
                if (pos != -1) { // Make sure this doesn't make it too long
                    before = line.substring(0, pos).trim();
                    if (fm.stringWidth(before) > maxWidth)
                        pos = findBreakBefore(line, guess);
                }
            }
            if (pos == -1)
                pos = guess; // Split in the middle of the word

            list.add(line.substring(0, pos).trim());
            line = line.substring(pos).trim();
            len = line.length();
        }
        if (len > 0)
            list.add(line);
    }

    /**
     * Returns the index of the first whitespace character or '-' in <var>line</var>
     * that is at or before <var>start</var>. Returns -1 if no such character is found. 
     * @param line A string of text
     * @param start Where to begin testing
     */
    public static int findBreakBefore(String line, int start) {
        for (int i = start; i >= 0; --i) {
            char c = line.charAt(i);
            if (Character.isWhitespace(c) || c == '-')
                return i;
        }
        return -1;
    }

    /**
     * Returns the index of the first whitespace character or '-' in <var>line</var>
     * that is at or after <var>start</var>. Returns -1 if no such character is found.
     * @param line A string of text
     * @param start Where to begin testing
     */
    public static int findBreakAfter(String line, int start) {
        int len = line.length();
        for (int i = start; i < len; ++i) {
            char c = line.charAt(i);
            if (Character.isWhitespace(c) || c == '-')
                return i;
        }
        return -1;
    }
}
Returns an ArrayList of strings, one for each line in the string after it has been wrapped to fit lines of maxWidth. This code assumes str is not null. - Java java.lang

Description

Demo Code

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