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  1. import java.util.*;
  2.  
  3. public class Main {
  4.  
  5.     public static boolean isValidJson(Object input) {
  6.         if (!(input instanceof Map)) return false;
  7.         return checkMap((Map<?, ?>) input);
  8.     }
  9.  
  10.     private static boolean checkMap(Map<?, ?> map) {
  11.         for (Map.Entry<?, ?> entry : map.entrySet()) {
  12.             if (!(entry.getKey() instanceof String)) return false;
  13.  
  14.             Object value = entry.getValue();
  15.             if (value == null || value instanceof String || value instanceof Number || value instanceof Boolean) {
  16.                 continue;
  17.             } else if (value instanceof Map) {
  18.                 if (!checkMap((Map<?, ?>) value)) return false;
  19.             } else if (value instanceof List) {
  20.                 if (!checkList((List<?>) value)) return false;
  21.             } else {
  22.                 return false;
  23.             }
  24.         }
  25.         return true;
  26.     }
  27.  
  28.     private static boolean checkList(List<?> list) {
  29.         for (Object item : list) {
  30.             if (item == null || item instanceof String || item instanceof Number || item instanceof Boolean) {
  31.                 continue;
  32.             } else if (item instanceof Map) {
  33.                 if (!checkMap((Map<?, ?>) item)) return false;
  34.             } else if (item instanceof List) {
  35.                 if (!checkList((List<?>) item)) return false;
  36.             } else {
  37.                 return false;
  38.             }
  39.         }
  40.         return true;
  41.     }
  42.  
  43.     public static void main(String[] args) {
  44.         // Valid
  45.         Map<String, Object> valid = new HashMap<>();
  46.         valid.put("user", Map.of("name", "A", "age", 30));
  47.  
  48.         valid.put("tags", Arrays.asList("java", 123, true, null));
  49.  
  50.         System.out.println(isValidJson(valid)); // true
  51.  
  52.         // tidak valid  key bukan String
  53.         Map<Object, Object> invalid1 = new HashMap<>();
  54.         invalid1.put(123, "abc");
  55.         System.out.println(isValidJson(invalid1)); // false
  56.  
  57.         // tidak valid  ada tipe aneh (Date)
  58.         Map<String, Object> invalid2 = new HashMap<>();
  59.         invalid2.put("time", new Date());
  60.         System.out.println(isValidJson(invalid2)); // false
  61.     }
  62. }
  63.  
Success #stdin #stdout 0.12s 52720KB
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Standard input is empty
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true
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false
https://ideone.com/6zx2RE
language:
Java (HotSpot 12)
created:
10 days ago
visibility:
public

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