Java USES regular expressions to intercept the contents between specified strings:

package com.accord.util;

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * 正则表达式匹配两个字符串之间的内容
 * @author Administrator
 *
 */
public class RegexUtil {
	
	public static void main(String[] args) {
		String str = "<?xml version='1.0' encoding='UTF-8'?><ufinterface billtype='gl' filename='e:\1.xml' isexchange='Y' proc='add' receiver='1060337@1060337-003' replace='Y' roottag='sendresult' sender='01' successful='Y'><sendresult><billpk></billpk><bdocid>w764</bdocid><filename>e:\1.xml</filename><resultcode>1</resultcode><resultdescription>单据w764开始处理...单据w764处理完毕!</resultdescription><content>2017.09-记账凭证-1</content></sendresult><sendresult><billpk></billpk><bdocid>w1007</bdocid><filename>e:\1.xml</filename><resultcode>1</resultcode><resultdescription>单据w1007开始处理...单据w1007处理完毕!</resultdescription><content>2017.10-记账凭证-1</content></sendresult><sendresult><billpk></billpk><bdocid>w516</bdocid><filename>e:\1.xml</filename><resultcode>1</resultcode><resultdescription>单据w516开始处理...单据w516处理完毕!</resultdescription><content>2017.07-记账凭证-50</content></sendresult></ufinterface>";
		//String str = "abc3443abcfgjhgabcgfjabc";  
		String rgex = "<bdocid>(.*?)</bdocid>";
		
	    System.out.println((new RegexUtil()).getSubUtil(str,rgex)); 
	    List<String> lists = (new RegexUtil()).getSubUtil(str,rgex);
	    for (String string : lists) {
			System.out.println(string);
		}
	    System.out.println((new RegexUtil()).getSubUtilSimple(str, rgex));  
	}
	
	/** 
     * 正则表达式匹配两个指定字符串中间的内容 
     * @param soap 
     * @return 
     */  
    public List<String> getSubUtil(String soap,String rgex){  
        List<String> list = new ArrayList<String>();  
        Pattern pattern = Pattern.compile(rgex);// 匹配的模式  
        Matcher m = pattern.matcher(soap);  
        while (m.find()) {  
            int i = 1;  
            list.add(m.group(i));  
            i++;  
        }  
        return list;  
    }  
      
    /** 
     * 返回单个字符串，若匹配到多个的话就返回第一个，方法与getSubUtil一样 
     * @param soap 
     * @param rgex 
     * @return 
     */  
    public String getSubUtilSimple(String soap,String rgex){  
        Pattern pattern = Pattern.compile(rgex);// 匹配的模式  
        Matcher m = pattern.matcher(soap);  
        while(m.find()){  
            return m.group(1);  
        }  
        return "";  
    }  
}

operation results:

[w764, w1007, w516]
w764
w1007
w516
w764