java按钮左对齐 java左对齐命令

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();
 }
 @Override
 public Object parseObject(String source, ParsePosition pos) {
 // TODO Auto-generated method stub
 return source;
 }}