Example usage for java.util HashMap HashMap

Introduction

In this page you can find the example usage for java.util HashMap HashMap.

Prototype

public HashMap()

Source Link

Document

Constructs an empty HashMap with the default initial capacity (16) and the default load factor (0.75).

Usage

From source file:Main.java

public static void main(String[] a) {

    Map<String, String> map = new HashMap<String, String>();
    map.put("key1", "value1");
    map.put("key2", "value2");
    map.put("key3", "value3");

    System.out.println(map.get("key2"));
    System.out.println(map.containsKey("key2"));
    System.out.println(map.containsKey("key4"));
}

From source file:Main.java

public static void main(String args[]) {
    HashMap<Integer, String> newmap = new HashMap<Integer, String>();

    // populate hash map
    newmap.put(1, "tutorials");
    newmap.put(2, "from");
    newmap.put(3, "java2s.com");

    System.out.println("Map value before change: " + newmap);

    // put new values at key 3
    String prevvalue = (String) newmap.put(3, "is great");

    // check returned previous value
    System.out.println("Returned previous value: " + prevvalue);

    System.out.println("Map value after change: " + newmap);
}

From source file:Main.java

public static void main(String args[]) {

    HashMap<Integer, String> newmap2 = new HashMap<Integer, String>();
    HashMap<Integer, String> newmap1 = new HashMap<Integer, String>();

    // populate hash map
    newmap1.put(1, "tutorials");
    newmap1.put(2, "from");
    newmap1.put(3, "java2s.com");

    System.out.println("Values in newmap1: " + newmap1);

    // put all values in newmap2
    newmap2.putAll(newmap1);/*from w ww. j  a  v  a 2  s .c  om*/

    System.out.println("Values in newmap2: " + newmap2);
}

From source file:Main.java

public static void main(String[] args) {
    Map<Integer, String> map = new HashMap<>();

    for (int i = 0; i < 10; i++) {
        map.putIfAbsent(i, "val" + i);
    }/*  w ww. jav a 2  s  . c o  m*/

    map.forEach((id, val) -> System.out.println(val));
}

From source file:Main.java

public static void main(String... args) {
    Map<String, MyData> map = new HashMap<String, MyData>();
    map.put("A", new MyData());

    System.out.println(map);//www . j  a va2s . c om
}

From source file:Main.java

public static void main(String[] a) {

    HashMap<String, String> map = new HashMap<String, String>();
    map.put("key1", "value1");
    map.put("key2", "value2");
    map.put("key3", "value3");
    map.remove("key3");

    System.out.println(map);// w  w w  .j a v  a  2s.c  om
}

From source file:Main.java

public static final void main(String[] args) {
    Map<String, String> map = new HashMap<>();
    map.put("one", "a");
    System.out.println("Size = " + map.size());
    map.put(null, "b");
    System.out.println("Size = " + map.size());
    System.out.println("map.get(null) = " + map.get(null));
}

From source file:Main.java

public static void main(String[] args) {
    Map<String, String> map = new HashMap<>();
    map.put("CSS", "style");
    map.put("HTML", "mark up");
    map.put("Oracle", "database");
    map.put("XML", "data");

    map.forEach((String key, String value) -> {
        System.out.println("key=" + key + ",  value=" + value);
    });/*ww w .  ja  va 2 s.  co  m*/

}

From source file:Main.java

public static void main(String[] args) {
    Map<Integer, String> map = new HashMap<>();

    for (int i = 0; i < 10; i++) {
        map.putIfAbsent(i, "val" + i);
    }/*from   w  ww . j a v a  2  s. com*/

    map.forEach((id, val) -> System.out.println(val));

    System.out.println(map.getOrDefault(42, "not found")); // not found
}

From source file:Main.java

public static void main(String[] a) {
    Map<String, String> map = new HashMap<String, String>();
    map.put("key1", "value1");
    map.put("key2", "value2");
    map.put("key3", "value3");
    map.put(null, null);//from w w  w . ja v a 2s  . c o m

    Map<String, String> map2 = new HashMap<String, String>();
    map2.put("key4", "value4");
    map2.put("key5", "value5");
    map2.put("key6", "value6");
    map.putAll(map2);

    System.out.println(map);
}