@@ -36,7 +36,16 @@ public V get(K key){
3636 return node .val ;
3737 }
3838
39- // public void replace(K key, V oldVal, )
39+ 40+ public boolean replaceIfExists (K key , V oldVal , V newVal ){
41+ int ind = getIndex (key );
42+ if (buckets [ind ] == null ){
43+ return false ;
44+ }
45+ return buckets [ind ].replaceIfExist (key , oldVal , newVal );
46+ }
47+ 48+ 4049
4150 public V delete (K key ){
4251 int ind = getIndex (key );
@@ -50,6 +59,14 @@ public V delete(K key){
5059 return node .val ;
5160 }
5261
62+ public boolean insertIfAbsent (K key , V val ){
63+ int ind = getIndex (key );
64+ if (buckets [ind ] == null ){
65+ return false ;
66+ }
67+ return buckets [ind ].insertIfAbsent (key , val );
68+ }
69+ 5370 private int getIndex (K key ){
5471 int hash = key .hashCode ();
5572 return hash %bucketCount ;
@@ -102,6 +119,52 @@ void updateNode(Node<K, V> node){
102119 }
103120 }
104121
122+ boolean replaceIfExist (K key , V oldVal , V newVal ){
123+ rLock .lock ();
124+ try {
125+ Node <K , V > node = start ;
126+ while (node != null ) {
127+ if (node .key .equals (key ) && node .val .equals (oldVal )){
128+ node .val = newVal ;
129+ return true ;
130+ }
131+ node = node .next ;
132+ }
133+ return false ;
134+ }finally {
135+ rLock .unlock ();
136+ }
137+ }
138+ 139+ 140+ boolean insertIfAbsent (K key , V val ){
141+ wLock .lock ();
142+ try {
143+ Node <K , V > node = start ;
144+ boolean found = false ;
145+ while (node != null ) {
146+ if (node .key .equals (key )) {
147+ found = true ;
148+ }
149+ node = node .next ;
150+ }
151+ if (!found ){
152+ Node <K , V > newNode = new Node <>(key , val );
153+ if (start == null ){
154+ start = newNode ;
155+ end = newNode ;
156+ }else {
157+ end .next = newNode ;
158+ newNode .prev = end ;
159+ end = newNode ;
160+ }
161+ }
162+ return !found ;
163+ }finally {
164+ wLock .unlock ();
165+ }
166+ }
167+ 105168 /*
106169 * returns node if node.key.equals(key)
107170 * else returns null
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