Last requirement

Question about the task

Under discussion

I tried it on my own, then compared my approach with the ones in the forums but it still doesn't validate. Output is as required. Can anyone help please?

Build part of a WHERE query using StringBuilder.
If a parameter is null, then it shouldn't be included in the query.

Example:

{name=Johnson, country=United States, city=Los Angeles, age=null}

Result:

name = 'Johnson' and country = 'United States' and city = 'Los Angeles'

Requirements:

The getQuery method must have one Map parameter.
The getQuery method must return a String.
The getQuery method must be static.
The getQuery method must return a string built according to the rules specified in the task conditions.

package com.codegym.task.task22.task2208; import java.util.Map; import java.util.HashMap; import java.util.Formatter; public class Solution { public static void main(String[] args) { Map<String, String> map = new HashMap<>(); map.put("name", "Johnson"); map.put("country", "United States"); map.put("city", "Los Angeles"); map.put("age", null); System.out.println(getQuery(map)); } public static String getQuery(Map<String, String> params) { String[] arr = {"name", "country", "city", "age"}; StringBuilder sb = new StringBuilder(); Formatter fm = new Formatter(sb); int i = 0; for (String s : arr) { for(Map.Entry<String, String> me : params.entrySet()){ if (me.getKey().equalsIgnoreCase(arr[i])&& me.getValue()!=null){ fm.format("%s = '%s'",arr[i], me.getValue()); i++; if(i != params.size()-1) { sb.append(" and "); } } } } return sb.toString(); } }

Comments (7)

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Premachandran

Level 35 , Ernakulam, India

10 February 2020, 12:21

need not make it so complicated. if you avoid the string array and string comparisons it will become simple, iterate through the map. if either the key or the value is empty, skip it by using continue statement. else append them to the string builder with = in between and "and' at the end. after iteration remove the last "and" convert to string and return

Sarah Suß

Level 25 , Hamburg, Germany

14 February 2020, 15:17

So I tried different variations of your advice even opted for a different cropping method for the StringBuilder. Still won't pass the last condition.

import java.util.Map;
import java.util.LinkedHashMap;
import java.util.Formatter;



public class Solution {
    public static void main(String[] args) {
        Map<String, String> map = new LinkedHashMap<>();
        map.put("name", "Johnson");
        map.put("country", "United States");
        map.put("city", "Los Angeles");
        map.put("age", null);
        System.out.println(getQuery(map));
    }

    public static String getQuery(Map<String, String> params) {

        StringBuilder sb = new StringBuilder();
	        Formatter fm = new Formatter(sb);
	        int i = 0;

	         for(Map.Entry<String, String> me : params.entrySet()){

	        	 if (me.getValue()==null){


	        		continue;

	        	}else if(i != params.size()-1) {
	        	        fm.format("%s = '%s'",me.getKey(), me.getValue());
	        			sb.append(" and ");
	        			i++;
	        	}
	        }

	        sb.delete(sb.lastIndexOf(" and "), sb.length());
	        String ns = sb.toString();
	        return ns;
    }
}

Guadalupe Gagnon

Level 37 , Tampa, United States

14 February 2020, 18:58

"If a parameter is null, then it shouldn't be included in the query." in the above code when you add a null key into the map, such as " map.put(null, "Los Angeles"); ", it will print: null = 'Los Angeles'

Premachandran

Level 35 , Ernakulam, India

15 February 2020, 14:47

StringBuilder sb = new StringBuilder(); if (params == null || params.isEmpty()) return sb.toString(); for (Map.Entry<String, String> entry : params.entrySet()) { if (entry.getValue() == null || entry.getKey() == null) continue; sb.append(entry.getKey()).append(" = '").append(entry.getValue()).append("' and "); } if (sb.length() > 5) sb.delete(sb.length() - 5, sb.length()); return sb.toString(); }

Johannes

Level 27 , Centurion, Pretoria, South-Africa

28 April 2020, 06:55

hi Guada, I have the same problem. I thought maps could not have a null key ? But even if I add the check for both not = null, it fails ? The results I got were exactly the same as when I copy the code from Premachandran in above comment, but I had negative logic if (entry.getKey() != null && entry.getValue() != null) { sb.append(entry.getKey()).append(" = '").append(entry.getValue()).append("' and "); counter ++; } if (counter ==0 ) return ""; And it only validated with the other way around. Very irritating validator.

Guadalupe Gagnon

Level 37 , Tampa, United States

28 April 2020, 13:44

@Johannes Maps can hold null values as either a key or values. This is because collections (such as ArrayLists, HashSets, HashMaps) are always collections of objects and objects can have null values. In Maps, both the key and value have to be objects. Primitives (such as int, boolean, short) can not be null, but you can not make a collection of primitives. So: :

HashSet<int> test = new HashMap<>(); // compiler will complain because collection of primitives
HashSet<Integer> test1 = new HashMap<>(); // Non-primitive is used, compiler is happy

Now a couple errors with the code you shared: first, if a null value is present in the first pulled map entry then 'counter' would be 0 when the last line is reached and a blank string would be returned. If you put null in as a key, the internal sorting would most likely put that at the very first index, thus guaranteeing that this problem would occur. The second error is that (when the first entry doesn't include null) the returned string would end with: " and ". It should end with: = 'entry.getValue()' If you fixed these issues then your code would pass.

Johannes

Level 27 , Centurion, Pretoria, South-Africa

28 April 2020, 14:17

Thanks, I did pass it before I commented, but I had to modify the mentioned code. I do check to delete the last "and", but the counter problem you mention, is interesting. Thanks for the update ;)