Alter JSON string

// Given
{"00020001":{"vr":"OB","InlineBinary":"AAE="},"00020002":{"vr":"UI","Value":["1.2.840.10008.5.1.4.1.1.2"]},

// Desired
{"00020001":{"vr":"OB","InlineBinary":"AAE=","tagname":"value1"},"00020002":{"vr":"UI","Value":["1.2.840.10008.5.1.4.1.1.2"],"tagname":"value2"},

Using Java
No 3rd party JSON libraries

Call a provided java function with the tag to get the tagname
public static String getTagName(String tag)
ex
String tagname = getTagName("00020003");
// tagname has the value "value3"
update the JSON string