public class LongestSubString {    public static void main(String args[]){    	String arg = "abacdefgafg";    	System.out.println(longestSubStr(arg));    }        public static String longestSubStr(String str){    	StringBuilder sb = new StringBuilder(str);    	char[] cs = str.toCharArray();    	String maxStr = "";    	StringBuilder tmpStr = new StringBuilder();    	for(int i = 0; i < cs.length; i++){    		if(tmpStr.indexOf(String.valueOf(cs[i])) >= 0){    			if(maxStr.length() < tmpStr.length()){    				maxStr = tmpStr.toString();    			} else {    				tmpStr.delete(0, tmpStr.indexOf(String.valueOf(cs[i])));    				tmpStr.append(cs[i]);    			}    		} else {    			tmpStr.append(cs[i]);    		}    	}    	if(tmpStr.length() > maxStr.length()){    		maxStr = tmpStr.toString();    	}    		    	return maxStr;    }}