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Commit8c2cbd3

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author
jsquared21
committed
Add Ex_27_02
1 parent90d8a24 commit8c2cbd3

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7 files changed

+357
-0
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7 files changed

+357
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2.4 KB
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/*******************************************************************************
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* (Implement MyMap using open addressing with quadratic probing) Create a new *
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* concrete class that implements MyMap using open addressing with quadratic *
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* probing. For simplicity, use f(key) = key % size as the hash function, where *
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* size is the hash-table size. Initially, the hash-table size is 4. The table *
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* size is doubled whenever the load factor exceeds the threshold (0.5). *
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*******************************************************************************/
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publicclassExercise_27_02 {
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publicstaticvoidmain(String[]arg) {
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// Create a map
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MyMap<String,Integer>map =newMyHashMap<>();
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map.put("Smith",30);
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map.put("Anderson",31);
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map.put("Lewis",29);
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map.put("Cook",29);
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map.put("Tom",21);
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map.put("Mark",21);
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map.put("Smith",65);
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map.put("William",21);
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System.out.println("Entries in map: " +map);
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System.out.println("The age of Lewis is " +
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map.get("Lewis"));
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System.out.println("The age of William is " +
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map.get("William"));
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System.out.println("Is Smith in the map? " +
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map.containsKey("Smith"));
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System.out.println("Is Jay in the map? " +
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map.containsKey("Jay"));
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System.out.println("Is age 33 in the map? " +
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map.containsValue(33));
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System.out.println("Is age 31 in the map? " +
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map.containsValue(31));
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System.out.print("Keys in map: ");
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for (Stringkey :map.keySet()) {
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System.out.print(key +" ");
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}
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System.out.println();
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System.out.print("Values in map: ");
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for (intvalue :map.values()) {
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System.out.print(value +" ");
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}
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System.out.println();
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map.remove("Smith");
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System.out.println("Entries in map " +map);
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map.clear();
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System.out.println("Entries in map " +map);
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}
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}
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importjava.util.ArrayList;
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publicclassMyHashMap<K,V>implementsMyMap<K,V> {
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// Define the default hash-table size. Must be a power of 2
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privatestaticintDEFAULT_INITIAL_CAPACITY =4;
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// Define the maximum hash-table size. 1 << 30 is same as 2^30
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privatestaticintMAXIMUM_CAPACITY =1 <<30;
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// Current hash-table capacity. Capacity is a power of 2
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privateintcapacity;
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// Define default load factor
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privatestaticfloatDEFAULT_MAX_LOAD_FACTOR =0.5f;
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// Specify a load factor used in the hash table
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privatefloatloadFactorThreshold;
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// The number of entries in the map
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privateintsize =0;
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// Hash table is an ArrayList
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ArrayList<MyMap.Entry<K,V>>table;
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/** Construct a map with the default capacity and load factor */
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publicMyHashMap() {
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this(DEFAULT_INITIAL_CAPACITY,DEFAULT_MAX_LOAD_FACTOR);
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}
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/** Construct a map with the specified initial capacity and
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* default load factor */
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publicMyHashMap(intinitialCapacity) {
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this(initialCapacity,DEFAULT_MAX_LOAD_FACTOR);
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}
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/** Construct a map with the specified initial capacity
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* and load factor */
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publicMyHashMap(intinitialCapacity,floatloadFactorThreshold) {
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if (initialCapacity >MAXIMUM_CAPACITY)
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this.capacity =MAXIMUM_CAPACITY;
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else
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this.capacity =trimToPowerOf2(initialCapacity);
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this.loadFactorThreshold =loadFactorThreshold;
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table =newArrayList<>();
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for (inti =0;i <capacity;i++) {
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table.add(null);
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}
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}
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@Override/** Remove all of the entries from this map */
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publicvoidclear() {
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size =0;
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removeEntries();
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}
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@Override/** Return true if the specified key is in the map */
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publicbooleancontainsKey(Kkey) {
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if (get(key) !=null)
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returntrue;
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else
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returnfalse;
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}
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@Override/** Return true if this map contains the value */
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publicbooleancontainsValue(Vvalue) {
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for (inti =0;i <capacity;i++) {
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if (table.get(i) !=null &&table.get(i).getValue() ==value)
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returntrue;
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}
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returnfalse;
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}
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@Override/** Return a set of entries in the map */
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publicjava.util.Set<MyMap.Entry<K,V>>entrySet() {
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java.util.Set<MyMap.Entry<K,V>>set =
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newjava.util.HashSet<>();
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for (inti =0;i <capacity;i++) {
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if (table.get(i) !=null) {
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set.add(table.get(i));
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}
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}
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returnset;
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}
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@Override/** Return the value that matches the specified key */
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publicVget(Kkey) {
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intindex =hash(key.hashCode());
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inti =index -1;// One cycle of the arraylist
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intj =0;
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while (index !=i && (table.get(index) ==null ||
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table.get(index).getKey() !=key)) {
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index +=Math.pow(j++,2);
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index %=capacity;
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}
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if (table.get(index).getKey() ==key)
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returntable.get(index).getValue();
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returnnull;
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}
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@Override/** Return true if this map contains no entries */
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publicbooleanisEmpty() {
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returnsize ==0;
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}
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@Override/** Return a set consisting of the keys in this map */
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publicjava.util.Set<K>keySet() {
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java.util.Set<K>set =newjava.util.HashSet<>();
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for (inti =0;i <capacity;i++) {
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if (table.get(i) !=null) {
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set.add(table.get(i).getKey());
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}
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}
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returnset;
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}
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@Override/** Add an entry (key, value) into the map */
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publicVput(Kkey,Vvalue) {
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intindex =hash(key.hashCode());
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intj =0;
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while (table.get(index) !=null) {
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// Add a new entry (key, value)
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if (table.get(index).getKey() ==key) {
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Entry<K,V>entry =table.get(index);
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VoldValue =entry.getValue();
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// Replace old value with new value
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entry.value =value;
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table.set(index,entry);
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// Return the old value for the key
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returnoldValue;
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}
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index +=Math.pow(j++,2);
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index %=capacity;
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}
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// Check load factor
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if (size >=capacity *loadFactorThreshold) {
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if (capacity ==MAXIMUM_CAPACITY)
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thrownewRuntimeException("Exceeding maximum capacity");
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rehash();
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}
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// Add a new entry(key, value) to hashtable
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table.set(index,newMyMap.Entry<K,V>(key,value));
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size++;// Increase size
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returnvalue;
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}
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@Override/** Remove the entry for the specified key */
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publicvoidremove(Kkey) {
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intindex =hash(key.hashCode());
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inti =index -1;// One cycle of the arraylist
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intj =0;
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while ((table.get(index) ==null ||
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table.get(index).getKey() !=key) &&i !=index) {
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index +=Math.pow(j++,2);
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index %=capacity;
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}
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if (table.get(index).getKey() ==key)
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table.remove(index);
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}
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@Override/** Return the number of entries in this map */
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publicintsize() {
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returnsize;
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}
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@Override/** Return a set consisting of values in this map */
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publicjava.util.Set<V>values() {
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java.util.Set<V>set =newjava.util.HashSet<>();
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for (inti =0;i <capacity;i++) {
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if (table.get(i) !=null)
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set.add(table.get(i).getValue());
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}
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returnset;
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}
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/** Hash function */
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privateinthash(inthashCode) {
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returnsupplementalHash(hashCode) & (capacity -1);
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}
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/** Ensure the hashing is evenly distributed */
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privatestaticintsupplementalHash(inth) {
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h ^= (h >>>20) ^ (h >>>12);
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returnh ^ (h >>>7) ^ (h >>>4);
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}
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/** Return a power of 2 for initialCapacity */
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privateinttrimToPowerOf2(intinitialCapacity) {
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intcapacity =1;
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while (capacity <initialCapacity) {
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capacity <<=1;
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}
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returncapacity;
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}
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/** Remove all entries from map */
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privatevoidremoveEntries() {
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table.clear();
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}
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/** Rehash the map */
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privatevoidrehash() {
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capacity <<=1;// Same as capacity *= 2. <= is more efficient
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for (inti = (size +1);i <capacity;i++) {
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table.add(null);
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}
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}
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@Override/** Return a string repersentation for this map */
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publicStringtoString() {
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StringBuilderbuilder =newStringBuilder("[");
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for (Entry<K,V>entry:table) {
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if (entry !=null &&table.size() >0)
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builder.append(entry);
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}
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builder.append("]");
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returnbuilder.toString();
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}
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}
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818 Bytes
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publicinterfaceMyMap<K,V> {
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/** Remove all of the entries form this map */
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publicvoidclear();
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/** Return true if the specified key is in the map */
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publicbooleancontainsKey(Kkey);
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/** Return true if this map sontains the specified value */
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publicbooleancontainsValue(Vvalue);
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/** Return a set of entries in the map */
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publicjava.util.Set<Entry<K,V>>entrySet();
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/** Return the value that matches the specified key */
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publicVget(Kkey);
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/** Return true if this map doesn't contain any entries */
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publicbooleanisEmpty();
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/** Return a set consisting of the keys in this map */
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publicjava.util.Set<K>keySet();
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/** Add an entry (key, value) into the map */
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publicVput(Kkey,Vvalue);
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/** Remove entry for the specified key */
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publicvoidremove(Kkey);
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/** Return the number of mappings in this map */
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publicintsize();
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/** Return a set consisting of the values in this map */
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publicjava.util.Set<V>values();
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/** Define an inner class for Entry */
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publicstaticclassEntry<K,V> {
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Kkey;
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Vvalue;
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publicEntry(Kkey,Vvalue) {
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this.key =key;
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this.value =value;
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}
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publicKgetKey() {
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returnkey;
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}
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publicVgetValue() {
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returnvalue;
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}
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@Override
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publicStringtoString() {
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return"[" +key +", " +value +"]";
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}
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}
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}

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