Mahout FastByIdMap 例子
FastByIdMap是基于散列的，在处理冲突时是线性探测而非分离链接，这样就不必为每一个条目增加一个Map.Entry对象，从而节省内存开销。下面代码是一个线性探测Map的Demo：
package com.example.mahout;
public class ArrayHashST_Linear_Probing<Key, Val> {
private int M = 30001;
private Key[] keys = (Key[]) new Object;
private Val[] vals = (Val[]) new Object;
private int hash(Key key) {
return (key.hashCode() & 0x7fffffff) % M;
}
public void put(Key key, Val val) {
int i;
for (i = hash(key); keys != null; i = (i + 1) % M)
if (keys.equals(key))
break;
keys = key;
vals = val;
}
public Val get(Key key) {
int i;
for (i = hash(key); keys != null; i = (i + 1) % M)
if (keys.equals(key))
break;
return vals;
}
public static void main(String[] args) {
ArrayHashST_Linear_Probing<String,String> st = new ArrayHashST_Linear_Probing<String, String>();
st.put("jocularly", "jocularly");
st.put("seriously", "seriously");
st.put("listen", "listen");
st.put("suburban", "suburban");
st.put("untravelled", "untravelled");
st.put("considerating", "considerating");
st.put("browsing","browsing");
System.out.println(st.get("jocularly"));
}
}
这个是分离链接的Demo：
package com.example.mahout;
public class ListHashST_Separate_Chaining<Key, Value> {
private int M = 8191;
private Node[] st = new Node;
private static class Node {
Object key;
Object val;
Node next;
Node(Object key, Object val, Node next) {
this.key = key;
this.val = val;
this.next = next;
}
}
private int hash(Key key) {
return (key.hashCode() & 0x7fffffff) % M;
}
public void put(Key key, Value val) {
int i = hash(key);
for (Node x = st; x != null; x = x.next) {
if (key.equals(x.key)) {
x.val = val;
return;
}
}
st = new Node(key, val, st);
}
public Value get(Key key) {
int i = hash(key);
//System.out.println(i);
for (Node x = st; x != null; x = x.next){
System.out.println(x.val);
if (key.equals(x.key))
return (Value) x.val;
}
return null;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
ListHashST_Separate_Chaining<String, String> st =new ListHashST_Separate_Chaining<String, String>();
st.put("jocularly", "jocularly");
st.put("seriously", "seriously");
st.put("listen", "listen");
st.put("suburban", "suburban");
st.put("untravelled", "untravelled");
st.put("considerating", "considerating");
st.put("browsing","browsing");
st.get("jocularly");
//System.out.println(st.get("jocularly"));
}
}
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