Java手写简易版HashMap的使用（存储+查找）

hashmap的基本结构

package com.liuyuhe;

public class node {
 int hash;
 object key;
 object value;
 node next;
}

package com.liuyuhe;

public class myhashmap {
 node[] table; //位桶数组
 int size; //存放键值对的个数
 public myhashmap() {
 table=new node[16];
 }
 
}

put()方法存储键值对

 public void put(object key,object value) {
 node newnode = new node();
 newnode.hash=myhash(key.hashcode(),table.length);
 newnode.key=key;
 newnode.value=value;
 newnode.next=null;
 node temp = table[newnode.hash];
 node iterlast=null;
 if(temp==null) {
  table[newnode.hash]=newnode;
 }else {
  while(temp!=null) {
  if(temp.key.equals(key)) {
   temp.value=value;
   return;
  }else {
   iterlast=temp;
   temp=temp.next;
  }
  }
  iterlast.next=newnode;
 }
 ++size;
 }
 public int myhash(int v,int length) {
 system.out.println("hash in myhash: "+(v&(length-1)));
 return v&(length-1);
 }

重写tostring()方法打印map内容

@override
 public string tostring() {
 stringbuilder sb = new stringbuilder();
 sb.append("{");
 boolean isfirst=true;
 //遍历数组
 for(int i=0;i<table.length;++i) {
  //遍历链表
  node temp = table[i];
  while(temp!=null) {
  if(isfirst) {
   isfirst=false;
   sb.append(temp.key+":"+temp.value);
  }else {
   sb.append(","+temp.key+":"+temp.value);
  }
  temp=temp.next;
  }
 }
 sb.append("}");
 return sb.tostring();
 }

get()方法查找键值对

public object get(object key) {
 int hash=myhash(key.hashcode(),table.length);
 object value=null;
 if(table[hash]!=null) {
  node temp=table[hash];
  while(temp!=null) {
  if(temp.key.equals(key)) {
   value=temp.value;
   break;
  }else {
   temp=temp.next;
  }
  }
 }
 return value;
 }

增加泛型（完整代码）

package com.liuyuhe;

public class node<k,v> {
 int hash;
 k key;
 v value;
 node next;
}

package com.liuyuhe;

public class myhashmap<k,v> {
 node[] table; //位桶数组
 int size; //存放键值对的个数
 public myhashmap() {
 table=new node[16];
 }
 public void put(k key,v value) {
 node newnode = new node();
 newnode.hash=myhash(key.hashcode(),table.length);
 newnode.key=key;
 newnode.value=value;
 newnode.next=null;
 node temp = table[newnode.hash];
 node iterlast=null;
 if(temp==null) {
  table[newnode.hash]=newnode;
 }else {
  while(temp!=null) {
  if(temp.key.equals(key)) {
   temp.value=value;
   return;
  }else {
   iterlast=temp;
   temp=temp.next;
  }
  }
  iterlast.next=newnode;
 }
 ++size;
 }
 @suppresswarnings("unchecked")
 public v get(k key) {
 int hash=myhash(key.hashcode(),table.length);
 v value=null;
 if(table[hash]!=null) {
  node temp=table[hash];
  while(temp!=null) {
  if(temp.key.equals(key)) {
   value=(v)temp.value;
   break;
  }else {
   temp=temp.next;
  }
  }
 }
 return value;
 }
 public int myhash(int v,int length) {
 system.out.println("hash in myhash: "+(v&(length-1)));
 return v&(length-1);
 }
 @override
 public string tostring() {
 stringbuilder sb = new stringbuilder();
 sb.append("{");
 boolean isfirst=true;
 //遍历数组
 for(int i=0;i<table.length;++i) {
  //遍历链表
  node temp = table[i];
  while(temp!=null) {
  if(isfirst) {
   isfirst=false;
   sb.append(temp.key+":"+temp.value);
  }else {
   sb.append(","+temp.key+":"+temp.value);
  }
  temp=temp.next;
  }
 }
 sb.append("}");
 return sb.tostring();
 }
}

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