如何从hashmap中检索键和值

Question

我试图通过对象将值插入哈希映射,我想检查是否将值插入到哈希映射中.所以我使用此代码但在运行时我无法获得任何输出.

怎么解决这个？

码:

import java.util.*;
import java.io.*;
import java.lang.*;

public class TaskList
{   

    private static HashMap<Integer, Object[]> dataz = new HashMap<Integer,Object[]>();
    private static  HashMap<Integer, Object[]> screen_dataz = new HashMap<Integer,Object[]>();
    public final static Object[][] longValues = {{"10", "kstc-proc", "10.10.10.10.10.","5","O"},{"11", "proc-lvk1", "12.1.2.","4","O"},{"13", "trng-lvk1", "4.6.1.","3","O"}};
    private static String sl,pid,tid,mval,status;

    public static void main(String args[])
    {
        addTask();
    }

    public static void addTask()
    {  
        for (int k=0; k<longValues.length; k++)
        {
        screen_dataz.put(k,longValues);
        }
        Set mapSet = (Set) screen_dataz.entrySet();
        Iterator mapIterator = mapSet.iterator();
        while (mapIterator.hasNext()) 
        {
        Map.Entry mapEntry = (Map.Entry) mapIterator.next();
        String keyValue = (String) mapEntry.getKey();
        String value = (String) mapEntry.getValue();
        System.out.println(value);
        }
    }
}

Answer 1

首先,您必须longValues在地图中添加一行矩阵,而不是整个矩阵:

 for (int k=0; k<longValues.length; k++)
 {
     screen_dataz.put(k,longValues[k]);
 }

然后,迭代时将值提取为Object[]和不提取String,并键入为Integer

 while (mapIterator.hasNext()) 
 {
     Map.Entry mapEntry = (Map.Entry) mapIterator.next();
     Integer keyValue = (Integer) mapEntry.getKey();
     Object[] value = (Object[]) mapEntry.getValue();
     //iterate over the array and print each value
     for (int i=0; i<value.length; i++) {
         System.out.print(value[i] + " ");
     }
     System.out.println();
 }

Answer 2

您的代码有一些修复/改进:

• 使用泛型时不要使用cast
• 添加元素的循环screen_dataz总是添加相同的对象

• 存储在地图中的值是一个数组,这意味着它不会像您期望的那样通过简单的调用打印出来 toString()

  public class TaskList {
      private static HashMap<Integer, String[]> dataz = new HashMap<Integer, String[]>();
      private static HashMap<Integer, String[]> screen_dataz = new HashMap<Integer, String[]>();
      public final static String[][] longValues = {
              { "10", "kstc-proc", "10.10.10.10.10.", "5", "O" },
              { "11", "proc-lvk1", "12.1.2.", "4", "O" },
              { "13", "trng-lvk1", "4.6.1.", "3", "O" } };
      private static String sl, pid, tid, mval, status;
  
      public static void main(String args[]) {
          addTask();
      }
  
      public static void addTask() {
          for (int k = 0; k < longValues.length; k++) {
              screen_dataz.put(k, longValues[k]);
          }
          Set<Entry<Integer, String[]>> mapSet = screen_dataz.entrySet();
          Iterator<Entry<Integer, String[]>> mapIterator = mapSet.iterator();
          while (mapIterator.hasNext()) {
              Entry<Integer, String[]> mapEntry = mapIterator.next();
              Integer keyValue = mapEntry.getKey();
              String[] value = mapEntry.getValue();
              System.out.println(Arrays.toString(value));
          }
      }
  }