On Apr 22, 7:17 pm, Sagarika <SonamSenSha...@[EMAIL PROTECTED]
> wrote:
> I am new in this group.So,if somehow my way of posting goes wrong
> please pardon.
>
> I made a program as MyHashTable described below.All I want to print
> all the elements in the hashtable as a string.What should I do? Can
> you help me?
>
> im****t java.io.*;
> im****t java.util.*;
> im****t java.util.Comparator;
>
> interface HashComparator{
> boolean isComparable(Object key);
> boolean isEqualTo(Object Key1,Object Key2);
> int hashValue(Object key);
> }
>
> interface HashTable {
> int size();
> boolean present(int p);
> boolean isEmpty(int e);
> Object key(int k);
> Object element(int e);
> Object findElement(Object key);
> void insert(Object key,Object element);
> Object removeElement(Object key);
> }
>
> class InvalidKeyException extends RuntimeException {
> InvalidKeyException(String message) {
> super(message);
> }
>
> }
>
> class HashTableFullException extends RuntimeException {
> HashTableFullException(String message) {
> super(message);
> }
>
> }
>
> class data {
> Object key,element;
>
> data() {
> key = null;
> element = null;
> }
>
> data(Object k,Object e){
> key = k;
> element = e;
> }
>
> public Object key(){ return key;}
> public Object element(){ return element; }
> public void setKey(Object k) { key = k; }
> public void setElement(Object e) { element = e; }
> }
>
> public class MyHashTable implements HashTable {
>
> static data PRESENT = new data();
>
> int m,n;
>
> data[] bucket;
> Object NON_EXISTENT_KEY;
>
> private static HashComparator C;
>
> public MyHashTable(HashComparator C1){
> n = 0;
> C = C1;
> m = 200;
> bucket = new data[m];
> }
>
> public MyHashTable(HashComparator C1,int i){
> n = 0;
> C = C1;
> m = i;
> bucket = new data[m];
> }
>
> void examine(Object Key){
> try {
> if(!C.isComparable(Key)) throw new
> InvalidKeyException("The key is not valid");
> }
> catch(NullPointerException n) { }
> }
>
> public boolean present(int x){ return (bucket[x] ==
> PRESENT); }
>
> public boolean isEmpty(int y){ return (bucket[y] == null); }
>
> public Object key(int k) { return bucket[k].key();}
>
> public Object element(int e) { return bucket[e].element();}
>
> public int size() { return n; }
>
> int findData(Object key) throws InvalidKeyException {
> examine(key);
> int x = C.hashValue(key) % m;
> int y = x;
> do {
> if(isEmpty(x)) return -1;
> if(present(x)) x = (x+1) % m;
> else if (C.isEqualTo(key(x),key))
> return x;
> else
> x = (x+1) % m;
> }while(x != y);
> return -1;
> }
>
> public Object findElement (Object key) throws
> InvalidKeyException {
> int x = findData(key);
> if(x < 0) return this.NON_EXISTENT_KEY;
> return element(x);
> }
>
> public void insert(Object key,Object element) throws
> InvalidKeyException {
> examine(key);
> try {
> int x = C.hashValue(key) % m;
> int y = x;
> do {
> if(isEmpty(x) || present(x)) {
> bucket[x] = new data(key,element);
> return;
> }
> x = (x+1) % m;
> }while(x != y);
> throw new HashTableFullException("Hash table is full.
> ");
> }
> catch(NullPointerException n) { }
> n++;
> }
>
> public Object remove(Object key) throws InvalidKeyException{
> int x = findData(key);
> if(x<0) return this.NON_EXISTENT_KEY;
> Object O = element(x);
> bucket[x] = PRESENT;
> n--;
> return O;
> }
>
> public static void main(String[] args) {
> MyHashTable T = new MyHashTable(C);
> try{
> T.insert(new Integer(1),new Integer(29));
> T.insert(new Integer(2),new Integer(45));
> T.insert(new Integer(3),new Integer(37));
> T.insert(new Integer(4),new Integer(99));
> T.insert(new Integer(5),new Integer(58));
> T.insert(new Integer(6),new Integer(76));
> T.remove(new Integer(2));
> System.out.println(); System.out.println();
> System.out.println("The table size is " + T.size());
> System.out.println();
> }
> catch(InvalidKeyException e) {
> System.out.println("The key is Invalid");
> System.out.println(e.getMessage());
> }
> }
>
> }
I have implemented toString function but all that it prints all the
elements present in the hash table to be null why is it so?
im****t java.io.*;
im****t java.util.*;
im****t java.util.Comparator;
interface HashComparator{
boolean isComparable(Object key);
boolean isEqualTo(Object Key1,Object Key2);
int hashValue(Object key);
}
interface HashTable {
int size();
boolean present(int p);
boolean isEmpty(int e);
Object key(int k);
Object element(int e);
Object findElement(Object key);
void insert(Object key,Object element);
Object remove(Object key);
}
class InvalidKeyException extends RuntimeException {
InvalidKeyException(String message) {
super(message);
}
}
class HashTableFullException extends RuntimeException {
HashTableFullException(String message) {
super(message);
}
}
class data {
Object key,element;
data() {
key = null;
element = null;
}
data(Object k,Object e){
key = k;
element = e;
}
public Object key(){ return key;}
public Object element(){ return element; }
public void setKey(Object k) { key = k; }
public void setElement(Object e) { element = e; }
}
public class MyHashTable implements HashTable {
static data PRESENT = new data();
int m,n;
data[] bucket;
Object NON_EXISTENT_KEY;
private static HashComparator C;
public MyHashTable(HashComparator C1){
n = 0;
C = C1;
m = 200;
bucket = new data[m];
}
public MyHashTable(HashComparator C1,int i){
n = 0;
C = C1;
m = i;
bucket = new data[m];
}
void examine(Object Key){
try {
if(!C.isComparable(Key)) throw new
InvalidKeyException("The key is not valid");
}
catch(NullPointerException n) { }
}
public boolean present(int x){ return (bucket[x] ==
PRESENT); }
public boolean isEmpty(int y){ return (bucket[y] == null); }
public Object key(int k) { return bucket[k].key();}
public Object element(int e) { return bucket[e].element();}
public int size() { return n; }
int findData(Object key) throws InvalidKeyException {
examine(key);
int x = C.hashValue(key) % m;
int y = x;
do {
if(isEmpty(x)) return -1;
if(present(x)) x = (x+1) % m;
else if (C.isEqualTo(key(x),key))
return x;
else
x = (x+1) % m;
}while(x != y);
return -1;
}
public Object findElement (Object key) throws
InvalidKeyException {
int x = findData(key);
if(x < 0) return this.NON_EXISTENT_KEY;
return element(x);
}
public void insert(Object key,Object element) throws
InvalidKeyException {
examine(key);
try {
int x = C.hashValue(key) % m;
int y = x;
do {
if(isEmpty(x) || present(x)) {
bucket[x] = new data(key,element);
return;
}
x = (x+1) % m;
}while(x != y);
throw new HashTableFullException("Hash table is full.
");
}
catch(NullPointerException n) { }
n++;
}
public Object remove(Object key) throws InvalidKeyException{
int x = findData(key);
if(x < 0) return this.NON_EXISTENT_KEY;
Object O = element(x);
bucket[x] = PRESENT;
n--;
return O;
}
public String ConverttoString() {
StringBuffer s = new StringBuffer();
int i = 0;
int elements = this.size();
while(elements != 0) {
s.append(" " + this.bucket[i++]);
elements -- ;
}
return s.toString();
}
public static void main(String[] args) {
MyHashTable T = new MyHashTable(C);
try{
T.insert(new Integer(1),new Integer(29));
T.insert(new Integer(2),new Integer(45));
T.insert(new Integer(3),new Integer(37));
T.insert(new Integer(4),new Integer(99));
T.insert(new Integer(5),new Integer(58));
T.insert(new Integer(6),new Integer(76));
System.out.println(); System.out.println();
System.out.println("The table size is " + T.size());
System.out.println();
System.out.println("The table is "
+T.ConverttoString());
System.out.println();
}
catch(InvalidKeyException e) {
System.out.println("The key is Invalid");
System.out.println(e.getMessage());
}
}
}
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