Java map Examples

Programming Language: Java

Namespace/Package Name: java.util

Class/Type: map

Examples at hotexamples.com: 2

The java.util Map is a collection that stores key-value pairs in memory. It allows fast and efficient retrieval of values based on their corresponding keys. The Map interface is implemented by several classes in the Java standard library, including HashMap, TreeMap, and LinkedHashMap.

Example 1:

// Create a new HashMap object
Map wordCount = new HashMap<>();

// Add some key-value pairs
wordCount.put("apple", 3);
wordCount.put("banana", 2);
wordCount.put("orange", 5);

// Retrieve the value for a specific key
int count = wordCount.get("banana");

// Loop through all the keys and values
for (Map.Entry entry : wordCount.entrySet()) {
    System.out.println(entry.getKey() + ": " + entry.getValue());
}

In this example, we create a new HashMap object and add some key-value pairs representing word counts. We then retrieve the value for a specific key ("banana"), and loop through all the keys and values in the map.

This example uses the HashMap class from the java.util package.

Example 2:

// Create a new TreeMap object
Map nameToNumber = new TreeMap<>();

// Add some key-value pairs
nameToNumber.put(1, "Alice");
nameToNumber.put(2, "Bob");
nameToNumber.put(3, "Charlie");

// Remove a key-value pair
nameToNumber.remove(2);

// Check if a key is present in the map
boolean containsKey = nameToNumber.containsKey(3);

// Loop through all the values in the map
for (String name : nameToNumber.values()) {
    System.out.println(name);
}

In this example, we create a new TreeMap object and add some key-value pairs representing names and their corresponding numbers. We then remove a key-value pair from the map, check if a key is present, and loop through all the values in the map. This example uses the TreeMap class from the java.util package. Overall, the java.util Map provides a powerful and flexible way to store and retrieve key-value pairs in memory, with different implementations offering different features and performance characteristics.

Java map - 2 examples found. These are the top rated real world Java examples of java.util.map extracted from open source projects. You can rate examples to help us improve the quality of examples.

Frequently Used Methods

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put(2)

Example #1

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File: testtxn.java Project: moorecoin/MooreClient

 private string maketx(string tx_blob) throws exception {
   map<string, object> data = new hashmap<>();
   data.put("id", 0);
   data.put("command", "submit");
   data.put("tx_blob", tx_blob);
   string postdata = new gson().tojson(data);
   string json = moorecoinwebsocketclient.request(postdata);
   system.out.println("make tx result: " + json);
   return json;
 }

Example #2

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File: SmallSortedMapTest.java Project: moorecoin/MooreCoinService

  public void testmakeimmutable() {
    smallsortedmap<integer, integer> map = smallsortedmap.newinstancefortest(3);
    for (int i = 0; i < 6; i++) {
      assertnull(map.put(i, i + 1));
    }
    map.makeimmutable();
    assertequals(new integer(1), map.get(0));
    assertequals(6, map.size());

    try {
      map.put(23, 23);
      fail("expected unsupportedoperationexception");
    } catch (unsupportedoperationexception expected) {
    }

    map<integer, integer> other = new hashmap<integer, integer>();
    other.put(23, 23);
    try {
      map.putall(other);
      fail("expected unsupportedoperationexception");
    } catch (unsupportedoperationexception expected) {
    }

    try {
      map.remove(0);
      fail("expected unsupportedoperationexception");
    } catch (unsupportedoperationexception expected) {
    }

    try {
      map.clear();
      fail("expected unsupportedoperationexception");
    } catch (unsupportedoperationexception expected) {
    }

    set<map.entry<integer, integer>> entryset = map.entryset();
    try {
      entryset.clear();
      fail("expected unsupportedoperationexception");
    } catch (unsupportedoperationexception expected) {
    }

    iterator<map.entry<integer, integer>> it = entryset.iterator();
    while (it.hasnext()) {
      map.entry<integer, integer> entry = it.next();
      try {
        entry.setvalue(0);
        fail("expected unsupportedoperationexception");
      } catch (unsupportedoperationexception expected) {
      }
      try {
        it.remove();
        fail("expected unsupportedoperationexception");
      } catch (unsupportedoperationexception expected) {
      }
    }

    set<integer> keyset = map.keyset();
    try {
      keyset.clear();
      fail("expected unsupportedoperationexception");
    } catch (unsupportedoperationexception expected) {
    }

    iterator<integer> keys = keyset.iterator();
    while (keys.hasnext()) {
      integer key = keys.next();
      try {
        keyset.remove(key);
        fail("expected unsupportedoperationexception");
      } catch (unsupportedoperationexception expected) {
      }
      try {
        keys.remove();
        fail("expected unsupportedoperationexception");
      } catch (unsupportedoperationexception expected) {
      }
    }
  }