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eazybyteseazybytes
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Map,HashMap,TreeMap,LinkedHashMap
1 parent 997f748 commit beae807

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‎section_20/.gitignore‎

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### IntelliJ IDEA ###
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out/
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!**/src/main/**/out/
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!**/src/test/**/out/
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### Eclipse ###
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.apt_generated
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.classpath
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.factorypath
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.project
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.settings
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.springBeans
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.sts4-cache
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bin/
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!**/src/main/**/bin/
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!**/src/test/**/bin/
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### NetBeans ###
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/nbproject/private/
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/nbbuild/
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/dist/
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/nbdist/
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/.nb-gradle/
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### VS Code ###
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.vscode/
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### Mac OS ###
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.DS_Store

‎section_20/src/com/eazybytes/map/HashMapDemo.java‎

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package com.eazybytes.map;
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import java.util.HashMap;
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import java.util.Map;
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public class HashMapDemo {
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public static void main(String[] args) {
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var countryMap = new HashMap<String,String>();
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countryMap.put("India", "New Delhi");
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countryMap.put("USA", "Washington, DC");
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countryMap.put("France", "Paris");
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countryMap.put(null, null);
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System.out.println(countryMap.get("India"));
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countryMap.remove(null);
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System.out.println(countryMap.size());
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}
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}

‎section_20/src/com/eazybytes/map/HashMapIterationDemo.java‎

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package com.eazybytes.map;
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import java.util.*;
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public class HashMapIterationDemo {
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public static void main(String[] args) {
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var countryMap = new HashMap<String,String>();
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countryMap.put("India", "New Delhi");
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countryMap.put("USA", "Washington, DC");
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countryMap.put("France", "Paris");
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approach3(countryMap);
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}
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public static void approach1(HashMap<String, String> countryMap) {
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Set<String> keys = countryMap.keySet();
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Iterator<String> iterator = keys.iterator();
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while (iterator.hasNext()) {
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String key = iterator.next();
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String capital = countryMap.get(key);
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System.out.println(key + " : "+capital);
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}
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/*for(String key:keys) {
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String capital = countryMap.get(key);
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System.out.println(key + " : "+capital);
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}*/
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}
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public static void approach2(HashMap<String, String> countryMap) {
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Set<Map.Entry<String, String>> entries = countryMap.entrySet();
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Iterator<Map.Entry<String, String>> iterator = entries.iterator();
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/*while (iterator.hasNext()) {
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Map.Entry<String,String> entry = iterator.next();
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String key = entry.getKey();
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String capital = entry.getValue();
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System.out.println(key + " : "+capital);
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}*/
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for(Map.Entry<String, String> entry:entries) {
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String key = entry.getKey();
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String capital = entry.getValue();
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System.out.println(key + " : "+capital);
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}
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}
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public static void approach3(HashMap<String, String> countryMap) {
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Collection<String> values = countryMap.values();
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for(String value:values) {
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System.out.println(value);
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}
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}
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}

‎section_20/src/com/eazybytes/map/ImmutableMapDemo.java‎

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package com.eazybytes.map;
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import java.util.Map;
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import static java.util.Map.entry;
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public class ImmutableMapDemo {
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public static void main(String[] args) {
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Map<String,Integer> stringIntegerMap = Map.of("a",1,"b",2,"c",3);
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processMap(stringIntegerMap);
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Map<Integer,String> integerStringMap = Map.ofEntries(entry(1, "Tom"),
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entry(2, "Dick"),
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entry(3, "Harry"));
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processMap1(integerStringMap);
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}
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public static void processMap(Map<String,Integer> stringIntegerMap) {
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for(Map.Entry<String,Integer> entry : stringIntegerMap.entrySet()){
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System.out.println(entry.getKey()+":"+entry.getValue());
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}
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}
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public static void processMap1(Map<Integer,String> integerStringMap) {
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for(Map.Entry<Integer,String> entry : integerStringMap.entrySet()){
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System.out.println(entry.getKey()+":"+entry.getValue());
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}
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}
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}

‎section_20/src/com/eazybytes/map/LinkedHashMapDemo.java‎

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package com.eazybytes.map;
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import java.util.LinkedHashMap;
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import java.util.Map;
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import java.util.SequencedMap;
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public class LinkedHashMapDemo {
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public static void main(String[] args) {
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LinkedHashMap<Integer,String> linkedHashMap = new LinkedHashMap<>();
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linkedHashMap.put(4, "Four");
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linkedHashMap.put(1, "One");
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linkedHashMap.put(7, "Seven");
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linkedHashMap.put(2, "Two");
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for(Map.Entry<Integer,String> entry : linkedHashMap.entrySet()) {
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System.out.println(entry.getKey()+":"+entry.getValue());
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}
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SequencedMap<Integer,String> reversedLinkedHashMap = linkedHashMap.reversed();
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for(Map.Entry<Integer,String> entry : reversedLinkedHashMap.entrySet()) {
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System.out.println(entry.getKey()+":"+entry.getValue());
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}
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}
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}

‎section_20/src/com/eazybytes/map/TreeMapDemo.java‎

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package com.eazybytes.map;
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import java.util.Map;
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import java.util.TreeMap;
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public class TreeMapDemo {
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public static void main(String[] args) {
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Map<Integer,String> numbers = new TreeMap<>();
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numbers.put(23, "Twenty three");
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numbers.put(12, "Twelve");
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numbers.put(42, "Forty two");
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numbers.put(3, "Three");
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numbers.put(19, "Nineteen");
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numbers.put(48, "Forty eight");
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numbers.put(76, "Seventy six");
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for(Map.Entry<Integer,String> entry : numbers.entrySet()){
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System.out.println(entry.getKey()+"-"+entry.getValue());
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}
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}
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}

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