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hmkcodehmkcode
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java map and list
java map and list
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‎java-list-map/.classpath‎

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<?xml version="1.0" encoding="UTF-8"?>
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<classpath>
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<classpathentry kind="src" path="src/test/java" output="target/test-classes" including="**/*.java"/>
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<classpathentry kind="src" path="src/main/java" including="**/*.java"/>
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<classpathentry kind="output" path="target/classes"/>
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<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
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<classpathentry kind="var" path="M2_REPO/junit/junit/3.8.1/junit-3.8.1.jar"/>
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</classpath>

‎java-list-map/pom.xml‎

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.hmkcode</groupId>
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<artifactId>java-list-map</artifactId>
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<version>1.0-SNAPSHOT</version>
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<packaging>jar</packaging>
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<name>java-list-map</name>
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<url>http://maven.apache.org</url>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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</properties>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>3.8.1</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎java-list-map/src/main/java/com/hmkcode/ListApp.java‎

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package com.hmkcode;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.LinkedList;
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import java.util.List;
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import com.hmkcode.vo.Person;
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public class ListApp
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{
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public static void main( String[] args )
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{
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// ( 1 ) List
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// A. Initiate
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List<Person> arrayList = new ArrayList<Person>();
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List<Person> linkedList = new LinkedList<Person>();
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// B. Populate
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for(Person person:getPersons()){
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arrayList.add(person);
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linkedList.add(person);
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}
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// --> print
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System.out.println("--------- Print All -------------");
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System.out.println("ArrayList: "+arrayList);
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System.out.println("LinkedList: "+linkedList);
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// C. Iterate
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System.out.println("--------- Print Iterate by index -------------");
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for(int i = 0; i < linkedList.size(); i++){
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System.out.println("LinkedList[ "+i+" ]"+linkedList.get(i));
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}
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System.out.println("--------- Print Iterate by for each -------------");
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//this is an efficient way to iterate
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for(Person person:linkedList){
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System.out.println("LinkedList: "+person);
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}
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// D. Sort
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Collections.sort(linkedList);
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// --> print
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System.out.println("--------- Print Sorted List -------------");
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System.out.println("Sorted LinkedList: "+linkedList);
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}
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private static Person[] getPersons(){
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Person[] persons = new Person[5];
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persons[0] = new Person("Brit", 29);
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persons[1] = new Person("John", 32);
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persons[2] = new Person("Jack", 27);
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persons[3] = new Person("Jenifer", 24);
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persons[4] = new Person("Brit", 37);
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return persons;
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}
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}

‎java-list-map/src/main/java/com/hmkcode/MapApp.java‎

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package com.hmkcode;
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import java.util.ArrayList;
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import java.util.Comparator;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.Map.Entry;
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import java.util.TreeMap;
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import com.hmkcode.vo.Person;
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public class MapApp
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{
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public static void main( String[] args )
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{
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// ( 1 ) Map
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// A. Initiate
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Map<String,Person> hashMap = new HashMap<String,Person>();
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Map<String,Person> treeMap = new TreeMap<String,Person>();
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// B. Populate
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int k = 0 ;
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for(Person person:getPersons()){
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hashMap.put(""+k,person);
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treeMap.put(""+k++,person);
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}
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// --> print
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System.out.println("--------- Print All -------------");
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System.out.println("HashMap: "+hashMap);
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System.out.println("TreeMap: "+treeMap);
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// C. Iterate
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// --> print
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System.out.println("--------- Print Iterate by get(key) -------------");
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for(String key:treeMap.keySet()){
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System.out.println("treeMap: [key: "+key+" , value: "+treeMap.get(key));
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}
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// --> print
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System.out.println("--------- Print Iterate by Entry -------------");
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for(Entry<String, Person> entry:treeMap.entrySet()){
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System.out.println("treeMap: [key: "+entry.getKey()+" , value: "+entry.getValue());
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}
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// D. Sort by value
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TreeMap<String,Person> sorted_map = new TreeMap<String,Person>(new ValueComparator());
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sorted_map.putAll(hashMap);
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// --> print
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System.out.println("--------- Print Sorted Map by Value -------------");
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System.out.println("Sorted HashMap: "+sorted_map);
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// E. Convert Map to List
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List<Person> persons = new ArrayList<Person>(sorted_map.values());
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// --> print
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System.out.println("--------- Print List<Person> -------------");
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System.out.println("List<Person>: "+persons);
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}
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private static Person[] getPersons(){
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Person[] persons = new Person[5];
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persons[0] = new Person("Brit", 29);
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persons[1] = new Person("John", 32);
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persons[2] = new Person("Jack", 27);
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persons[3] = new Person("Jenifer", 24);
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persons[4] = new Person("Brit", 37);
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return persons;
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}
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}
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class ValueComparator implements Comparator {
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Map map;
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public ValueComparator(){
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}
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public int compare(Object keyA, Object keyB){
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return ((String) keyA).compareTo((String) keyB);
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}
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}

‎java-list-map/src/main/java/com/hmkcode/vo/Person.java‎

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package com.hmkcode.vo;
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public class Person implements Comparable<Person> {
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private int age;
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private String name;
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public Person(String name, int age){
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this.name = name;
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this.age = age;
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}
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public int getAge() {
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return age;
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}
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public void setAge(int age) {
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this.age = age;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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@Override
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public String toString() {
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return "Person [age=" + age + ", name=" + name + "]";
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}
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@Override
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public int compareTo(Person person) {
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return this.age-person.getAge();
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}
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}

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