String 工具类

package com.util;

import java.text.DecimalFormat;
import java.util.Random;

/**
 * StringUtil.java
 * @author xiongmin
 */
public class StringUtil {
    
    /**
     * 生成一个定长的纯0字符串
     * @param length  字符串长度
     * @return 纯0字符串
     */
    public static String zeroString(int length) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < length; i++) {
            sb.append('0');
        }
        return sb.toString();
    }
    
    public static String toFixdLengthString(int num, int fixdlenth) {
        StringBuffer sb = new StringBuffer();
        String strNum = String.valueOf(num);
        if (fixdlenth - strNum.length() >= 0) {
            sb.append(StringUtil.zeroString(fixdlenth - strNum.length()));
        } else {
            throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！");
        }
        sb.append(strNum);
        return sb.toString();
    }
    
    public static String getUniqueString(int length){
 	   String str = "abcdefghijklmnopqrstvuwxyz0123456789ABCDEFGHIJKLMNOPQRSTVUWXYZ";
 	   int strLen = str.length();
 	   Random rand = new Random();
 	   StringBuilder sb = new StringBuilder();
 	   for(int i=0;i<length;i++){
 		   int index = rand.nextInt(strLen);
 		   sb.append(str.charAt(index));
 	   }
 	   return sb.toString();
    }
    
    
    /**
     *  将double数据保留两位小数
     * @param value
     * @param value2
     */
    public static String getDoubleTwo(String value) {  
        DecimalFormat df = new DecimalFormat("0.00");  
        double num1 = Double.parseDouble(value);  
        String back = df.format(num1);  
        
        return back;
    }  
    
    /**
     * 将字符串转换doule保留两位数据转换为百分比
     * @param value
     * @param value2
     */
    public static String getBaiFenBi(String value) {  
        DecimalFormat df = new DecimalFormat("0.00");  
        double num1 = Double.parseDouble(value);  
        String num2 = df.format(num1);  
        double num3 =  Double.parseDouble(num2) * 100;
        int num4 = (int)num3;
        String back = num4 + "%";
        
        return back;
    }  
    
    /**
     * 取两double值的商且保留两位小数
     * @param value
     * @param value2
     */
    public static String getHundred(String value, String value2) {  
        DecimalFormat df = new DecimalFormat("0.00");  
        double num1 = Double.parseDouble(value);  
        double num2 = Double.parseDouble(value2);  
        double num3;  
        if (num2 > 0) {  
            num3 = num1 / num2;  
        } else {  
            num3 = 0;  
        }  
        return df.format(num3);  
    }  
    
    /**
     * 取两double值的商且保留两位小数，转换为百分比，取绝对值
     * @param value
     * @param value2
     * @return
     */
    public static String getHundredBfb(String value, String value2) {  
        String str = getHundred(value,value2);
        double dou =  Double.parseDouble(str) * 100;
        int num = Math.abs((int)dou);
        String back = num + "%";
        return back;
    }  
    
    /**
     * null值转换
     * @return
     */
    public static String strNullZh(String str){
    	if(null == str || str.equals("")){
    		return "0";
    	}else{
    		return str;
    	}
    }
    
    
    public static void main(String[] args) {
    	long start = System.currentTimeMillis();
    	for(int i=0;i<10000;i++){
    		String s = StringUtil.getUniqueString(20);
            System.out.println(s); 
    	}
         
    	long end = System.currentTimeMillis();
    	System.out.println(end-start);
    }
}