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Arpit Bhardwaj
committed
Generics in Collections
1 parent 869997b commit eb3b7fa

12 files changed

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‎src/main/java/com/ab/generics/basic/GenericCircularBuffer.java‎

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package com.ab.generics.basic;
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public class GenericCircularBuffer<T> {
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private T[] buffer;
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private int readCursor = 0;
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private int writeCursor = 0;
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public GenericCircularBuffer(int size) {
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this.buffer = (T[]) new Object[size];
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}
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public boolean offer(T value){
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if(buffer[writeCursor] != null){
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return false;
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}
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buffer[writeCursor] = value;
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writeCursor = next(writeCursor);
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return true;
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}
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public T poll(){
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T value = buffer[readCursor];
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if(value != null){
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buffer[readCursor] = null;
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readCursor = next(readCursor);
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}
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return value;
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}
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public int next(int index){
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return (index+1)%buffer.length;
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}
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}

‎src/main/java/com/ab/generics/basic/StringCircularBuffer.java‎

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package com.ab.generics.basic;
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public class StringCircularBuffer {
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private String[] buffer;
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private int readCursor = 0;
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private int writeCursor = 0;
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public StringCircularBuffer(int size) {
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this.buffer = new String[size];
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}
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public boolean offer(String value){
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if(buffer[writeCursor] != null){
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return false;
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}
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buffer[writeCursor] = value;
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writeCursor = next(writeCursor);
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return true;
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}
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public String poll(){
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String value = buffer[readCursor];
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if(value != null){
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buffer[readCursor] = null;
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readCursor = next(readCursor);
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}
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return value;
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}
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public int next(int index){
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return (index+1)%buffer.length;
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}
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}

‎src/main/java/com/ab/generics/basic/TypeSafeExample.java‎

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package com.ab.generics.basic;
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public class TypeSafeExample {
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public static void main(String[] args) {
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GenericCircularBuffer<String> buffer = new GenericCircularBuffer<String>(10);
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buffer.offer("a");
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buffer.offer("bc");
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buffer.offer("d");
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//buffer.offer(1); //Leads to compile time error
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String value = concatenate(buffer);
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System.out.println(value);
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}
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private static String concatenate(GenericCircularBuffer<String> buffer) {
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StringBuilder result = new StringBuilder();
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String value;
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while((value = buffer.poll()) != null){
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result.append(value);
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}
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return result.toString();
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}
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}

‎src/main/java/com/ab/generics/basic/TypeStringExample.java‎

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package com.ab.generics.basic;
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public class TypeStringExample {
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public static void main(String[] args) {
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StringCircularBuffer buffer = new StringCircularBuffer(10);
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buffer.offer("a");
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buffer.offer("bc");
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buffer.offer("d");
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//buffer.offer(1); //Leads to Compile time error
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String value = concatenate(buffer);
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System.out.println(value);
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}
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private static String concatenate(StringCircularBuffer buffer) {
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StringBuilder result = new StringBuilder();
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String value;
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while((value = buffer.poll()) != null){
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result.append(value);
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}
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return result.toString();
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}
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}

‎src/main/java/com/ab/generics/basic/TypeUnsafeExample.java‎

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buffer.offer("bc");
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buffer.offer("d");
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//buffer.offer(1); //Leads to ClassCastException
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String value = concatenate(buffer);
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System.out.println(value);
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}

‎src/main/java/com/ab/generics/classes_and_interfaces/AgeComparator.java‎

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package com.ab.generics.classes_and_interfaces;
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import com.ab.generics.model.Person;
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import java.util.Comparator;
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public class AgeComparator implements Comparator<Person> {
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@Override
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public int compare(Person o1, Person o2) {
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return Integer.compare(o1.getAge(),o2.getAge());
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//return -1 * Integer.compare(o1.getAge(),o2.getAge()); for sorting in descending order
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}
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}

‎src/main/java/com/ab/generics/classes_and_interfaces/ReverseComparator.java‎

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package com.ab.generics.classes_and_interfaces;
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import java.util.Comparator;
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public class ReverseComparator<T> implements Comparator<T> {
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private final Comparator<T> delegateComparator;
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public ReverseComparator(Comparator<T> delegateComparator) {
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this.delegateComparator = delegateComparator;
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}
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@Override
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public int compare(T o1, T o2) {
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return -1 * delegateComparator.compare(o1, o2);
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}
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}

‎src/main/java/com/ab/generics/classes_and_interfaces/SortingExample.java‎

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package com.ab.generics.classes_and_interfaces;
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import com.ab.generics.model.Person;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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public class SortingExample {
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public static void main(String[] args) {
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Person donDrapper = new Person("Don Drapper", 89);
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Person peggyOlson = new Person("Peggy Olson", 65);
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Person bertCooper = new Person("Bert Cooper", 100);
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List<Person> madMen = new ArrayList<>();
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madMen.add(donDrapper);
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madMen.add(peggyOlson);
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madMen.add(bertCooper);
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System.out.println(madMen);
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Collections.sort(madMen,new AgeComparator());
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System.out.println(madMen);
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Collections.sort(madMen, new ReverseComparator<>(new AgeComparator()));
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System.out.println(madMen);
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}
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}

‎src/main/java/com/ab/generics/collections/ListExamples.java‎

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package com.ab.generics.collections;
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import com.ab.generics.model.Person;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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public class ListExamples {
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public static void main(String[] args) {
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Person donDrapper = new Person("Don Drapper", 89);
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Person peggyOlson = new Person("Peggy Olson", 65);
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List<Person> madMen = new ArrayList<Person>();
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madMen.add(donDrapper);
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madMen.add(peggyOlson);
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System.out.println(madMen);
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madMen.add(new Person("Bert Cooper", 100));
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//madMen.add(new Object());
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System.out.println(madMen);
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for (int i = 0; i < madMen.size(); i++) {
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final Person person = madMen.get(i);
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System.out.println(person);
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}
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final Iterator<Person> iterator = madMen.iterator();
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while (iterator.hasNext()){
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final Person person = iterator.next();
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System.out.println(person);
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}
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for (Person person:madMen) {
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System.out.println(person);
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}
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}
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}

‎src/main/java/com/ab/generics/collections/MapExamples.java‎

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package com.ab.generics.collections;
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import com.ab.generics.model.Person;
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import java.util.HashMap;
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import java.util.Map;
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public class MapExamples {
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public static void main(String[] args) {
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Person donDrapper = new Person("Don Drapper", 89);
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Person peggyOlson = new Person("Peggy Olson", 65);
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Person bertCooper = new Person("Bert Cooper", 100);
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Map<String, Person> madMen = new HashMap<>();
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madMen.put(donDrapper.getName(),donDrapper);
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//madMen.put(donDrapper.getName(),peggyOlson);//override the value in the key
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madMen.put(peggyOlson.getName(),peggyOlson);
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madMen.put(bertCooper.getName(),bertCooper);
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System.out.println(madMen);
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for (String name:madMen.keySet()) {
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System.out.println(name);
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}
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for (Person person:madMen.values()) {
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System.out.println(person);
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}
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for (Map.Entry<String,Person> entry:
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madMen.entrySet()) {
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//System.out.println(entry);
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System.out.println(entry.getKey());
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System.out.println(entry.getValue());
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}
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}
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}

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