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POKey not found in a HashMap for a composite object
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copied!<p>So, I made my own composite key in Java with 3 members </p> <pre><code>public class MyOwnKey{ int location; int length; String [] tokens; } </code></pre> <p>Now I create two objects using the constructor</p> <pre><code>String [] tokens = "Stackoverflow is great".split("\\s+"); Object key1 = new MyOwnKey(0,0,tokens) tokens = "Web is great".split("\\s+"); Object key2 = new MyOwnKey(0,0,tokens) </code></pre> <p>Now, I add the key in HashMap HashMap map = new HashMap(); map.put(key1,1);</p> <p>Now, this is the problem when I do contains key, it gives false;</p> <pre><code>**map.containsKey(key2) //returns false whereas it should return true.** </code></pre> <p>Just so that it makes sense:</p> <pre><code>key1.equals(key2) returns true </code></pre> <p>and the hashcode codes are also equal. <code>key1.hashCode() == key2.hashCode().</code> </p> <p>I have implemeneted my own version of hashCode, toEquals() and toCompare(). </p> <p>Not sure what's the problem.</p> <p>Here is the code</p> <pre><code>import java.io.DataOutput; import java.io.DataInput; import java.io.IOException; import org.apache.hadoop.io.WritableComparable; public class PatternGeneratorKey implements WritableComparable<Object> { private String [] tokens; int location; int length; StringBuffer _toString = null; public PatternGeneratorKey(){ tokens = new String[1]; location =0; length=1; } public PatternGeneratorKey(int location, int length, String [] tokens){ this.location = location; this.length = length; this.tokens= new String[tokens.length]; for(int i = 0; i < tokens.length;i++){ this.tokens[i] = tokens[i]; } } public int compareTo(Object o) { if (!(o instanceof PatternGeneratorKey)) return -1; return this.compareTo((PatternGeneratorKey) o); } public void write(DataOutput out) throws IOException { out.writeInt(tokens.length); for(int i = 0; i<tokens.length;i++){ out.writeUTF(tokens[i]); } out.writeInt(location); out.writeInt(length); } public void readFields(DataInput in) throws IOException { int l = in.readInt(); tokens = new String[l]; for(int i = 0; i < l ; i++){ tokens[i] = in.readUTF(); } location = in.readInt(); length = in.readInt(); } public int compareTo(PatternGeneratorKey k) { if(this.tokens.length - this.length != k.tokens.length - k.length){ return this.tokens.length - this.length -( k.tokens.length - k.length); } if(this.location != k.location){ return this.location - k.location; } int i = 0 , j= 0; for(i = 0, j=0 ; i < this.tokens.length && j < k.tokens.length;){ if(i == this.location ){ i = i + length; continue; } if( j == k.location){ j = j + k.length; continue; } if(!this.tokens[i].equalsIgnoreCase(k.tokens[j])){ return this.tokens[i].compareTo(k.tokens[j]); }else{ i++; j++; } } //TODO: add comparison on left out phrase return 0; } public int hashCode() { int hashCode=0; for(int i = 0; i < tokens.length;){ if(i == location ){ i = i + length; continue; } hashCode += tokens[i++].hashCode(); } hashCode+= location + tokens.length; return hashCode; } public String toString(){ if(_toString == null){ _toString = new StringBuffer(); for(int k = 0; k < tokens.length ;k++){ if(k==location){ _toString.append(":").append(" "); k=k+length-1; }else{ _toString.append(tokens[k]).append(" "); } } } return _toString.toString(); } public boolean equals(PatternGeneratorKey k) { if(this.tokens.length - this.length == k.tokens.length - k.length && this.location == k.location){ //assume second one is larger String tokens[] = k.tokens; int length = k.length; int location = k.location; String [] tokens1 = this.tokens; int length1 = this.length; int location1 = this.location; //make the local variable point to the largest of the two if( this.tokens.length > k.tokens.length){ tokens = this.tokens; length = this.length; location = this.location; tokens1 = k.tokens; length1 = k.length; location1 = k.location; } int i = 0 , j= 0; for(i = 0, j=0 ; i < tokens.length;){ if(i == location ){ i = i + length; continue; } // if( j >= location1 && j<= location1 + length1 -1){ if( j == location1){ j = j + length1; continue; } if(!tokens[i++].equalsIgnoreCase(tokens1[j++])){ return false; } } return true; }else{ return false; } } } </code></pre> <p>And, this is the code I am testing on</p> <pre><code>import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import org.apache.hadoop.io.Text; public class Test { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub String value = "gm used cars"; // Compile all the words using regex String[] tokens = value.toString().split("\\s+"); //to find pattern we need atleast two words in the query if(tokens.length <=1){ return; } Map<PatternGeneratorKey,List> map = new HashMap<PatternGeneratorKey, List>(); for(int l = 1 ; l < tokens.length; l++){ for(int i = 0 ; i < tokens.length - (l-1); i++){ String hit = new String(getPhrase(l, i, tokens)); PatternGeneratorKey key1 = new PatternGeneratorKey(i, l, tokens); List list = null; for(int k = 0;k< tokens.length;k++){ System.out.println("i:" + i + ",l:" + l + ",tokens:" + tokens[k]); } System.out.println("hashcode:" + key1.hashCode()); if(!map.containsKey(key1)){ list = new ArrayList<String>(); map.put(key1, list); }else{ list = (List) map.get(key1); } list.add(hit); } } value = "ford used cars"; String[] tokens2= value.toString().split("\\s+"); PatternGeneratorKey key2 = new PatternGeneratorKey(0, 1, tokens); //run a sliding window for length 1 to tokens length -1 for(int l = 1 ; l < tokens2.length; l++){ //genereate token pairs with sliding window. for(int i = 0 ; i < tokens2.length - (l-1); i++){ //hit a single token or a + b if there are two. String hit = new String(getPhrase(l, i, tokens2)); PatternGeneratorKey key1 = new PatternGeneratorKey(i, l, tokens2); System.out.println(); System.out.println(key1.toString() + "|" + key2.toString() + "|"+ key1.equals(key2)); for(int k = 0;k< tokens2.length;k++){ System.out.println("i:" + i + ",l:" + l + ",tokens:" + tokens2[k]); } System.out.println("hashcode:" + key1.hashCode()); List list = null; if(!map.containsKey(key1)){ list = new ArrayList<String>(); map.put(key1, list); }else{ list = (List) map.get(key1); } list.add(hit); } } value = "ford used cars"; tokens= value.toString().split("\\s+"); PatternGeneratorKey key1 = new PatternGeneratorKey(0,1,tokens); tokens2 = "gm used cars".split("\\s+"); key2 = new PatternGeneratorKey(0,1,tokens2); System.out.println(key1.equals(key2)); System.out.println(key2.equals(key1)); System.out.println(key1.hashCode() ); System.out.println(key2.hashCode() ); System.out.println(map); } private static String getPhrase(int l, int i, String[] tokens){ StringBuffer strin = new StringBuffer(); int index = 0; for(index = i ; index < i+l;index++){ if(index < i+l-1){ strin.append(tokens[index]).append("+"); } else { strin.append(tokens[index]); } } return strin.toString(); } } </code></pre>

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