public   class   Test   { 

public   static   void   main(String[]   args)   { 
String   toReplace   =   "abcdefgabcdefgabcdefgabcdefg"; 
String   target   =   "efg"; 
String   replacement   =   "@"; 
toReplace   =   replaceAll(toReplace,   target,   replacement); 
System.out.println("Result:   "+toReplace); 
} 
/** 
  *   替换字符串中所有匹配的字符 
  *   @param   toReplace   待替换字符串 
  *   @param   target   要替换掉的字符串 
  *   @param   replacement   替换的字符串 
  *   @return 
  */ 
public   static   String   replaceAll(String   toReplace,   String   target,   String   replacement){ 
String   returnStr   =   new   String(toReplace); 
for(;;){ 
int   index   =   returnStr.indexOf(target); 
if(index==-1){ 
break; 
}else{ 
returnStr=returnStr.substring(0,   index)+replacement+returnStr.substring(index+target.length()); 
} 
} 
return   returnStr; 
} 
}

public class Test {

    public static void main(String[] args) {
        String toReplace = "abcdefgabcdefgabcdefgabcdefg";
        String target = "efg";
        String replacement = "@";
        toReplace = replaceAll(toReplace, target, replacement);
        System.out.println("Result: "+toReplace);
    }
    /**
     * 替换字符串中所有匹配的字符
     * @param toReplace 待替换字符串
     * @param target 要替换掉的字符串
     * @param replacement 替换的字符串
     * @return
     */
    public static String replaceAll(String toReplace, String target, String replacement){
        String returnStr = new String(toReplace);
        for(;;){
            int index = returnStr.indexOf(target);
            if(index==-1){
                break;
            }else{
                returnStr=returnStr.substring(0, index)+replacement+returnStr.substring(index+target.length());
            }
        }
        return returnStr;
    }
}

import java.util.ArrayList;
import java.util.List;


public class Tester {
    public static void main(String[] args) {
        String toSplit="abcdefghijkefglmopefgqrs";
        String target = "efg";
        String[] result = split(toSplit, target, 2);
        for(int i=0;i<result.length;i++){
            System.out.println(i+"\t"+result[i]);
        }
    }
    public static String[] split(String toSplit, String target, int limit){
        List list = new ArrayList();
        for(int index = toSplit.indexOf(target);limit>1&&index!=-1;limit--,index = toSplit.indexOf(target)){
            list.add(toSplit.substring(0, index));
            toSplit = toSplit.substring(index+target.length());
        }
        list.add(toSplit);
        return (String[])list.toArray(new String[0]);
    }
}