Java知识积累1-StringAlign实现文字居中左右对齐

import java.text.*;public class StringAlign extends Format{public static final int JUST_LEFT='l'; //左对齐常量public static final int JUST_RIGHT='r'; //右对齐常量public static final int JUST_CENTER='c'; //居中常量PRivate int just; //当前的对其private int maxChars;public StringAlign(int maxChars,int just){switch (just) {case JUST_CENTER:case JUST_LEFT:case JUST_RIGHT:this.just=just;break;default:throw new IllegalArgumentException("invalid justification arg.");}if(maxChars<0){throw new IllegalArgumentException("必须是正数！");}this.maxChars=maxChars;}public StringBuffer format(Object obj,StringBuffer where,FieldPosition ignore){String s=(String)obj;String wanted=s.substring(0, Math.min(s.length(), maxChars));//如果没有空间用于对齐，则返回最大行宽的内容if(wanted.length()>maxChars){where.append(wanted);}else switch (just) {case JUST_RIGHT:pad(where,maxChars-wanted.length());where.append(wanted);break;case JUST_LEFT:where.append(wanted);pad(where,maxChars-wanted.length());break;case JUST_CENTER:int startPos=where.length();pad(where,(maxChars-wanted.length())/2);where.append(wanted);pad(where,(maxChars-wanted.length())/2);//调整化整误差pad(where,maxChars-(where.length()-startPos));break;

}return where;}protected final void pad(StringBuffer to,int howMany){for(int i=0;i<howMany;i++){to.append(' ');}}String format(String s){return format(s,new StringBuffer(),null).toString();}@Overridepublic Object parSEObject(String source, ParsePosition pos) {// TODO Auto-generated method stubreturn source;}

}