account.java

字符串对齐工具

/**
 * 
 */
package StringAlign;

/**
 * @author Owner
 *
 */
public class account {
	public static final int JUST_LEFT = 0; //左对齐

	public static final int JUST_RIGHT = 2; //右对齐

	public static final int JUST_CENTER = 1; //居中对齐

	private int just; //当前对齐格式

	private int maxChars; //一行的最大长度

	/** */
	/** 默认构造函数 */
	public account() {
		//默认为居中对齐，一行的最大长度为80
		this.just = JUST_CENTER;
		this.maxChars = 80;
	}

	/** */
	/** 构造一个字符串对齐器，需要传入一行的最大长度和对齐的格式 */
	public account(int maxChars, int just) {
		this(); //首先构造一个默认字符串对其器
		//根据传入参数修改字符串对齐器的属性
		this.setJust(just);
		this.setMaxChars(maxChars);
	}

	public int getJust() {
		return just;
	}

	/** */
	/** 设置字符串对齐器的对齐格式 */
	public void setJust(int just) {
		switch (just) {
		case JUST_LEFT:
		case JUST_RIGHT:
		case JUST_CENTER:
			this.just = just;
			break;
		default:
			System.out.println("invalid justification arg.");
		}
	}

	public int getMaxChars() {
		return maxChars;
	}

	/** */
	/** 设置字符串对齐器的一行最大字符数 */
	public void setMaxChars(int maxChars) {
		if (maxChars < 0) {
			System.out.println("maxChars must be positive.");
		} else {
			this.maxChars = maxChars;
		}
	}

	/** */
	/** 对齐一个字符串 */
	public String format(String s) {
		StringBuffer where = new StringBuffer();
		//从待对其的字符串中取出一段子字符串，子串长度为行最大长度和s长度的较小值
		int wantedLength = Math.min(s.length(), this.maxChars);
		String wanted = s.substring(0, wantedLength);
		//根据对齐模式，将空格插入到合适的位置
		switch (this.just) {
		case JUST_LEFT:
			//左对齐，将空格插入到字符串的右边
			where.append(wanted);
			pad(where, maxChars - wantedLength);
			break;
		case JUST_RIGHT:
			//右对齐，将空格插入到字符的左边
			pad(where, maxChars - wantedLength);
			where.append(wanted);
			break;
		case JUST_CENTER:
			//居中对齐，将空格平均插入到字符串的两边
			int startPos = where.length();
			pad(where, (maxChars - wantedLength) / 2);
			where.append(wanted);
			pad(where, (maxChars - wantedLength) / 2);
			//调整舍入误差
			pad(where, maxChars - (where.length() - startPos));
			break;
		}
		//如果原字符串长度大于一行的最大长度，则将余下部分放入下一行
		if (s.length() > wantedLength) {
			String remainStr = s.substring(wantedLength);
			where.append("\r\n" + this.format(remainStr));
		}
		return where.toString();
	}

	/** */
	/** 在to后面append howMany个空格字符 */
	protected final void pad(StringBuffer to, int howMany) {
		for (int i = 0; i < howMany; i++) {
			to.append(" ");
		}
	}

}