Java代码实现哈希表（google 公司的上机题）

public class HashTableDemo {

 public static void main(String[] args) {
  
  HashTable hashTable = new HashTable(7);
  
  String key = "";
  Scanner scanner = new Scanner(System.in);
  while(true) {
  
   System.out.println("add:添加雇员");
   System.out.println("list:查看雇员");
   System.out.println("find:查找雇员");
   System.out.println("del:删除雇员");
   System.out.println("exit:退出");
     
   key = scanner.next();
   switch (key) {
   case "add":
    System.out.println("请输入id：");
    int id = scanner.nextInt();
    System.out.println("请输入名字:");
    String name = scanner.next();
    
    Emp emp = new Emp(id, name);
    hashTable.add(emp);
    break;
   case "list":
    hashTable.list();
    break;
   case "find":
    System.out.println("请输入id:");
    int id2 = scanner.nextInt();
    hashTable.findEmpById(id2);
    break;
   case "del":
    System.out.println("请输入id:");
    int id3 = scanner.nextInt();
    hashTable.del(id3);
    break;
   case "exit":
    System.exit(10);
   default:
    break;
   }
  }
 }
}

// emp
class Emp{
 public int id;
 public String name;
 public Emp next;
 public Emp(int id, String name) {
  super();
  this.id = id;
  this.name = name;
 }
}

// EmpLinkedList
class EmpLinkedList{
 // 头指针，执行第一个Emp，因此我们这个链表的head，是直接指向第一个Emp
 private Emp head;
 
 // id是自增长的
 public void add(Emp emp) {
  // 如果是添加一个雇员
  if(head == null) {
   head = emp;
   return;
  }
  // 如果不是第一个
  Emp curEmp = head;
  while(true) {
   if(curEmp.next == null) {
    break;
   }
   curEmp = curEmp.next;
  }
  curEmp.next = emp;
 }
 
 public void list(int no) {
  if(head == null) {
   System.out.println("第" + (no+1) + "条链表为空！");
   return;
  }
  System.out.println("第" + (no+1) + "条链表信息为：");
  Emp curEmp = head;
  while(true) {
   System.out.printf("=> id=%d name=%s\t",curEmp.id,curEmp.name);
   if(curEmp.next == null) {
    break;
   }
   curEmp = curEmp.next;
  }
  System.out.println();
 }
 
 // 根据id查找雇员
 public Emp findEmpByid(int id) {
  if(head == null) {
   System.out.println("链表为空");
   return null;
  }
  Emp curEmp = head;
  while(true) {
   if(curEmp.id == id) {
    break;
   }
   if(curEmp.next == null) {
    System.out.println("遍历完了，没有找到！");
    curEmp = null;
    break;
   }
   curEmp = curEmp.next;
  }
  return curEmp;
 }
 
 // 根据id进行删除
 public boolean del(int id) {
  boolean flag = false;
  if(head == null) {
   System.out.println("当前链表为空！");
   return flag;
  }
  if(head.id == id) {
   head = null;
   flag = true;
   return flag;
  }
  Emp curEmp = head;
  while(true) {
   // 找到了改雇员
   if(curEmp.next.id == id) {
    curEmp.next = curEmp.next.next;
    curEmp.next = null;
    return (flag == false);
   }
   // 没有找到
   if(curEmp.next == null) {
    System.out.println("没有找改雇员！");
    curEmp = null;
    return flag;
   }
   curEmp = curEmp.next;
  }
 }
}

// 哈希表
class HashTable{
 
 private EmpLinkedList[] empLinkedListArr;
 private int size;
 public HashTable(int size) {
  super();
  this.size = size;
  empLinkedListArr = new EmpLinkedList[size];
  
  for(int i = 0; i < size; i++){
   empLinkedListArr[i] = new EmpLinkedList();
  }
 }
 
 // 添加雇员
 public void add(Emp emp) {
  // 根据员工的id得到改员工应该添加到哪条链表
  int empLinkedListNo = hashFun(emp.id);
  // 将emp添加到对应的链表中
  empLinkedListArr[empLinkedListNo].add(emp);
 }
 
 public void list() {
  for (int i = 0; i < empLinkedListArr.length; i++) {
   empLinkedListArr[i].list(i);
  }
 }
 
 public void findEmpById(int id) {
  int empLinkedListNo = hashFun(id);
  Emp emp = empLinkedListArr[empLinkedListNo].findEmpByid(id);
  if(emp != null) {
   System.out.println("在第" + (empLinkedListNo+1) + "条链表中找到id = " + id + "雇员");
  } else {
   System.out.println("在哈希表中没有找到");
  }
 }
 
 public void del(int id) {
  int empLinkedListNo = hashFun(id);
  boolean flag = empLinkedListArr[empLinkedListNo].del(id);
  if(flag == true) {
   System.out.println("在第" + (empLinkedListNo+1) + "条链表中删除了id = " + id + "雇员");
  } else {
   System.out.println("在哈希表中没有找到");
  }
  
 }
 
 public int hashFun(int id) {
  return id %size;
 }
}