165 lines
5.0 KiB
Java
165 lines
5.0 KiB
Java
package me.ehlxr.utils;
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/**
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* Created by lixiangrong on 2017/8/17.
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* 字符串对齐器。可以指定对齐格式和一行的最大字符数 对齐格式有左对齐、居中、右对齐
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*/
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public class StringAlign {
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/**
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* 左对齐格式
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*/
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public static final int JUST_LEFT = 0;
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/**
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* 居中格式
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*/
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public static final int JUST_CENTER = 1;
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/**
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* 右对齐格式
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*/
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public static final int JUST_RIGHT = 2;
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/**
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* 当前对齐格式
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*/
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private int just;
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/**
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* 一行的最大长度
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*/
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private int maxChars;
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/**
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* 默认构造函数
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*/
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public StringAlign() {
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// 默认为居中对齐
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this.just = JUST_CENTER;
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// 默认一行的最大长度为80
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this.maxChars = 80;
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}
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/**
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* 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。
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*
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* @param maxChars
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* @param just
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*/
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public StringAlign(int maxChars, int just) {
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// 首先构造一个默认字符串对齐器
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this();
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// 根据传入参数修改字符串对齐器的属性
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this.setJust(just);
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this.setMaxChars(maxChars);
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}
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public static void main(String[] args) {
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// 一行最多70个字符，居中显示。
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StringAlign formatter = new StringAlign(20, StringAlign.JUST_CENTER);
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// 比如显示页码
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System.out.println(formatter.format("- i -"));
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System.out.println(formatter.format(Integer.toString(444)));
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System.out.println(formatter.format("kkkkkkkkkkkkkkkkkkkkkkkkkkkk"));
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// 左对齐
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System.out.println();
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formatter = new StringAlign(20, StringAlign.JUST_LEFT);
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System.out.println(formatter.format("- i -") + "1");
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System.out.println(formatter.format(Integer.toString(444)) + "1");
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System.out.println(formatter.format("kkkkkkkkkkkkkkkkkkkkkkkkkkkk") + "1");
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// 右对齐
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System.out.println();
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formatter = new StringAlign(20, StringAlign.JUST_RIGHT);
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System.out.println(formatter.format("- i -"));
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System.out.println(formatter.format(Integer.toString(444)));
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System.out.println(formatter.format("kkkkkkkkkkkkkkkkkkkkkkkkkkkk"));
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}
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/**
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* 对齐一个字符串
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*
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* @param s 待对齐的字符串
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*/
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public String format(String s) {
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StringBuffer where = new StringBuffer();
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// 从待对齐的字符串中取出一段子字符串，子串的长度为行最大长度和s长度的较小值
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int wantedLength = Math.min(s.length(), this.maxChars);
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String wanted = s.substring(0, wantedLength);
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// 根据对齐模式，将空格放在合适的位置
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switch (this.just) {
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case JUST_RIGHT:
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// 如果是右对齐，那么将缺少的的字符用空格代替放在左边
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pad(where, maxChars - wantedLength);
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// 将字符串添加在右边
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where.append(wanted);
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break;
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case JUST_CENTER:
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// 居中对齐，将空格字符平均分在字符串两边。
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int startPos = where.length();
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pad(where, (maxChars - wantedLength) / 2);
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where.append(wanted);
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pad(where, (maxChars - wantedLength) / 2);
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// 调整舍入误差
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pad(where, maxChars - (where.length() - startPos));
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break;
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case JUST_LEFT:
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// 左对齐，将空格字符放在字符串右边。
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where.append(wanted);
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pad(where, maxChars - wantedLength);
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break;
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}
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// 如果原字符串的长度大于一行的最大长度，则将余下部分放入下一行
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if (s.length() > wantedLength) {
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String remainStr = s.substring(wantedLength);
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where.append("\n").append(this.format(remainStr));
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}
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return where.toString();
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}
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/**
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* 在to的后面append howMany个空格字符。
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*
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* @param to
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* @param howMany
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*/
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protected final void pad(StringBuffer to, int howMany) {
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for (int i = 0; i < howMany; i++)
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to.append(" ");
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}
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public int getJust() {
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return just;
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}
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/**
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* 设置字符串对齐器的对齐格式
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*
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* @param just
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*/
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public void setJust(int just) {
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switch (just) {
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case JUST_LEFT:
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case JUST_CENTER:
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case JUST_RIGHT:
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this.just = just;
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break;
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default:
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System.out.println("invalid justification arg.");
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}
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}
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public int getMaxChars() {
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return maxChars;
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}
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/**
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* 设置字符串对齐器的一行最大字符数
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*
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* @param maxChars
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*/
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public void setMaxChars(int maxChars) {
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if (maxChars < 0) {
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System.out.println("maxChars must be positive.");
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} else {
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this.maxChars = maxChars;
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}
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}
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}
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