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Text word wrapping in Java

There is a newer version: 0.1.12

package org.davidmoten.text.utils;

import java.util.Arrays;

final class StringBuilder2 implements CharSequence {

	private char[] chars;
	private int length;

	StringBuilder2(String s) {
		this(s.toCharArray(), s.length());
	}

	StringBuilder2() {
		this(new char[16], 0);
	}

	private StringBuilder2(char[] chars, int length) {
		this.chars = chars;
		this.length = length;
	}

	char[] internalArray() {
		return chars;
	}

	@Override
	public int length() {
		return length;
	}

	@Override
	public char charAt(int index) {
		return chars[index];
	}

	@Override
	public CharSequence subSequence(int start, int end) {
		char[] chars2 = new char[end - start];
		System.arraycopy(chars, start, chars2, 0, end - start);
		return new StringBuilder2(chars2, chars2.length);
	}

	public void append(StringBuilder2 s) {
		int len = s.length();
		checkSize(len);
		System.arraycopy(s.chars, 0, chars, length, len);
		length += len;
	}

	private void checkSize(int len) {
		if (length + len > chars.length) {
			chars = Arrays.copyOf(chars, chars.length * 2);
		}
	}

	public void setLength(int length) {
		this.length = length;
	}

	public void append(char ch) {
		checkSize(1);
		chars[length] = ch;
		length++;
	}

	public void delete(int start, int end) {
		System.arraycopy(chars, end, chars, start, length - end);
		length -= end - start;
	}

	public String substring(int start, int end) {
		return new String(chars, start, end - start);
	}

	@Override
	public String toString() {
		return new String(chars, 0, length);
	}

	/**
	 * Trims right space from this and returns {@code this}.
	 * 
	 * @return this
	 */
	StringBuilder2 rightTrim() {
		int i = length();
		while (i > 0) {
			if (!Character.isWhitespace(charAt(i - 1))) {
				break;
			}
			i--;
		}
		length = i;
		return this;
	}

}