java - How to retrieve data from nested hash-map in good view?

Java - How to retrieve data from nested hash-map in good view?

Retrieving data from a nested HashMap in Java can be done using nested loops or recursively. Here's an example of how you can retrieve data from a nested HashMap and print it in a readable format:

import java.util.HashMap; import java.util.Map; public class Main { public static void main(String[] args) { // Create a nested HashMap Map<String, Object> nestedMap = new HashMap<>(); nestedMap.put("key1", "value1"); Map<String, Object> innerMap = new HashMap<>(); innerMap.put("innerKey1", "innerValue1"); innerMap.put("innerKey2", "innerValue2"); nestedMap.put("key2", innerMap); // Print the nested map printNestedMap(nestedMap, ""); } public static void printNestedMap(Map<String, Object> map, String indent) { for (Map.Entry<String, Object> entry : map.entrySet()) { System.out.println(indent + entry.getKey() + ":"); if (entry.getValue() instanceof Map) { printNestedMap((Map<String, Object>) entry.getValue(), indent + " "); } else { System.out.println(indent + " " + entry.getValue()); } } } }

In this example:

  • We have a nested HashMap where the values can be either simple objects or nested HashMaps.
  • We define a method printNestedMap to print the nested HashMap recursively.
  • The method takes a map and an indent string as parameters.
  • It iterates over the entries of the map.
  • If the value of an entry is another map, it recursively calls printNestedMap with the inner map and an increased indent.
  • If the value is a simple object, it prints the key and value with the current indent.

This way, you can retrieve and print data from a nested HashMap in a readable format. Adjust the printing logic according to your specific requirements if needed.

Examples

  1. "Java nested HashMap traversal example"

    • Description: This query aims to understand how to traverse through a nested HashMap structure in Java effectively.
    • Code:
      public class NestedHashMapTraversal { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data for (Map.Entry<String, Map<String, Integer>> entry : nestedMap.entrySet()) { String outerKey = entry.getKey(); Map<String, Integer> innerMap = entry.getValue(); for (Map.Entry<String, Integer> innerEntry : innerMap.entrySet()) { String innerKey = innerEntry.getKey(); Integer value = innerEntry.getValue(); System.out.println("Outer Key: " + outerKey + ", Inner Key: " + innerKey + ", Value: " + value); } } } }

  2. "Java get value from nested HashMap by key"

    • Description: This query seeks to find a method to retrieve values from a nested HashMap using keys.
    • Code:
      public class NestedHashMapGetValue { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data String outerKey = "outerKey"; String innerKey = "innerKey"; if (nestedMap.containsKey(outerKey)) { Map<String, Integer> innerMap = nestedMap.get(outerKey); if (innerMap.containsKey(innerKey)) { Integer value = innerMap.get(innerKey); System.out.println("Value for key " + innerKey + " is: " + value); } } } }

  3. "Java iterate over nested HashMap"

    • Description: This query focuses on iterating over all elements within a nested HashMap in Java.
    • Code:
      public class NestedHashMapIteration { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data nestedMap.forEach((outerKey, innerMap) -> { innerMap.forEach((innerKey, value) -> { System.out.println("Outer Key: " + outerKey + ", Inner Key: " + innerKey + ", Value: " + value); }); }); } }

  4. "Java nested HashMap access example"

    • Description: This query seeks an example demonstrating how to access elements within a nested HashMap in Java.
    • Code:
      public class NestedHashMapAccess { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data String outerKey = "outerKey"; String innerKey = "innerKey"; if (nestedMap.containsKey(outerKey) && nestedMap.get(outerKey).containsKey(innerKey)) { Integer value = nestedMap.get(outerKey).get(innerKey); System.out.println("Value for key " + innerKey + " is: " + value); } } }

  5. "Java nested HashMap iteration"

    • Description: This query aims to find methods for iterating through a nested HashMap in Java.
    • Code:
      public class NestedHashMapIteration { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data for (String outerKey : nestedMap.keySet()) { Map<String, Integer> innerMap = nestedMap.get(outerKey); for (String innerKey : innerMap.keySet()) { Integer value = innerMap.get(innerKey); System.out.println("Outer Key: " + outerKey + ", Inner Key: " + innerKey + ", Value: " + value); } } } }

  6. "Java traverse nested HashMap"

    • Description: This query looks for ways to traverse a nested HashMap structure in Java efficiently.
    • Code:
      public class NestedHashMapTraversal { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data for (String outerKey : nestedMap.keySet()) { Map<String, Integer> innerMap = nestedMap.get(outerKey); for (String innerKey : innerMap.keySet()) { Integer value = innerMap.get(innerKey); System.out.println("Outer Key: " + outerKey + ", Inner Key: " + innerKey + ", Value: " + value); } } } }

  7. "Java retrieve value from nested HashMap"

    • Description: This query aims to find a method to retrieve values from a nested HashMap in Java.
    • Code:
      public class NestedHashMapGetValue { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data String outerKey = "outerKey"; String innerKey = "innerKey"; if (nestedMap.containsKey(outerKey)) { Map<String, Integer> innerMap = nestedMap.get(outerKey); if (innerMap.containsKey(innerKey)) { Integer value = innerMap.get(innerKey); System.out.println("Value for key " + innerKey + " is: " + value); } } } }

  8. "Java nested HashMap value retrieval"

    • Description: This query focuses on retrieving values from a nested HashMap structure in Java.
    • Code:
      public class NestedHashMapGetValue { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data String outerKey = "outerKey"; String innerKey = "innerKey"; Integer value = nestedMap.getOrDefault(outerKey, new HashMap<>()).get(innerKey); if (value != null) { System.out.println("Value for key " + innerKey + " is: " + value); } } }

  9. "Java nested HashMap data retrieval"

    • Description: This query seeks methods to retrieve data from a nested HashMap in Java.
    • Code:
      public class NestedHashMapDataRetrieval { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data String outerKey = "outerKey"; String innerKey = "innerKey"; Integer value = getValueFromNestedMap(nestedMap, outerKey, innerKey); if (value != null) { System.out.println("Value for key " + innerKey + " is: " + value); } } private static Integer getValueFromNestedMap(Map<String, Map<String, Integer>> nestedMap, String outerKey, String innerKey) { return nestedMap.containsKey(outerKey) ? nestedMap.get(outerKey).get(innerKey) : null; } }

  10. "Java nested HashMap accessing elements"

    • Description: This query aims to understand how to access elements within a nested HashMap in Java.
    • Code:
      public class NestedHashMapAccess { public static void main(String[] args) { Map<String, Map<String, Integer>> nestedMap = new HashMap<>(); // Populate nestedMap with data String outerKey = "outerKey"; String innerKey = "innerKey"; Integer value = nestedMap.getOrDefault(outerKey, new HashMap<>()).get(innerKey); if (value != null) { System.out.println("Value for key " + innerKey + " is: " + value); } } }

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