Thread: How to use recursion to parse groups inside groups in Java?

I'm just starting with recursion, so if someone can try to help I will very much appreciate it.

I have the following `String`:

    field1: typeA
    field2: typeA
    field3: typeB
    group1:
        fieldA: typeA
        fieldB: typeB
        subGroup1:
            fieldX: typeB
            fieldY: typeB
        fieldC: typeC
    field4: typeA
    group2:
        fieldA: typeB
        subGroup1:
            fieldX: typeA
            fieldY: typeA
        fieldB: typeA
        fieldC: typeC
    field5: typeC
    field6: typeD

Note that I can have groups inside groups (subgroups). I can also have groups inside groups inside groups, so recursion is mandatory as far as I know.

Note that the *spacing* in the beginning of each line determines if the field belongs to the group or not.

I would like to write a method in Java that will return a `LinkedHashMap<String, Object>`, where the *Object* map value can either be a `String` denoting that this is a field (not a group) or another `LinkedHashMap<String, Object>` denoting that this is a group (not a field).

I've tried but failed miserably. Recursion is just too hard for me at the moment, but I'm studying it.

To help whoever wants to help, below the code:

    	public static void main(String[] args) {
 
    		String text = String.join("\n",
 
    				"field1: typeA",
    				"field2: typeA",
    				"field3: typeB",
    				"group1:",
    				"    fieldA: typeA",
    				"    fieldB: typeB",
    				"    subGroup1:",
    				"        fieldX: typeB",
    				"        fieldY: typeB",
    				"    fieldC: typeC",
    				"field4: typeA",
    				"group2:",
    				"    fieldA: typeB",
    				"    subGroup1:",
    				"        fieldX: typeA",
    				"        fieldY: typeA",
    				"    fieldB: typeA",
    				"    fieldC: typeC",
    				"field5: typeC",
    				"field6: typeD",
 
    				"");
 
    		Map<String, Object> solution = doIt(text);
    		System.out.println(solution);
    	}
 
    	private static LinkedHashMap<String, Object> doIt(String text) {
    		// solution goes here...
    		return null;
    	}
    }

Can you post the code you tried?

I have nothing good to show. I got stuck, my brain went into a deadlock!


Here is the correct output:

    public static void main(String[] args) {
    	Map<String, Object> map = new LinkedHashMap<String, Object>();
 
    	map.put("field1", "typeA");
    	map.put("field2", "typeA");
    	map.put("field3", "typeB");
 
    	Map<String, Object> map2 = new LinkedHashMap<String, Object>();
    	map2.put("fieldA", "typeA");
    	map2.put("fieldB", "typeB");
 
    	Map<String, Object> map3 = new LinkedHashMap<String, Object>();
    	map3.put("fieldX", "typeB");
    	map3.put("fieldY", "typeB");
    	map2.put("subGroup1", map3);
 
    	map2.put("fieldC", "typeC");
 
    	map.put("group1", map2);
 
    	map.put("field4", "typeA");
 
    	Map<String, Object> map4 = new LinkedHashMap<String, Object>();
    	map4.put("fieldA", "typeB");
 
    	Map<String, Object> map5 = new LinkedHashMap<String, Object>();
    	map5.put("fieldX", "typeA");
    	map5.put("fieldY", "typeA");
    	map4.put("subGroup1", map5);
 
    	map4.put("fieldB", "typeA");
    	map4.put("fieldC", "typeC");
 
    	map.put("group2", map4);
 
    	map.put("field5", "typeC");
    	map.put("field6", "typeD");
 
    	System.out.println(map);
    }

The map matches the original text as you can see below:

{field1=typeA, field2=typeA, field3=typeB, group1={fieldA=typeA, fieldB=typeB, subGroup1={fieldX=typeB, fieldY=typeB}, fieldC=typeC}, field4=typeA, group2={fieldA=typeB, subGroup1={fieldX=typeA, fieldY=typeA}, fieldB=typeA, fieldC=typeC}, field5=typeC, field6=typeD}