看了学习视频,来一段代码
import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Set; public class jiheqiantao { public static void main(String[] args) { HashMap<String, String> javase = new HashMap<String, String>(); // 基础班 HashMap<String, String> javaee = new HashMap<String, String>(); // 就业班 javase.put("001", "张三"); javase.put("002", "李四"); javaee.put("001", "王五"); javaee.put("002", "赵六"); HashMap<String, HashMap<String, String>> czbk = new HashMap<String, HashMap<String, String>>(); czbk.put("基础班", javase); // 基础班对应一个HashMap集合 czbk.put("就业班", javaee); // 就业班对应一个HashMap集合 keySet(czbk); entrySet(czbk); } // 利用entrySet遍历,效率比keySet要高 public static void entrySet(HashMap<String, HashMap<String, String>> czbk) { Set<Map.Entry<String, HashMap<String, String>>> classNameSet = czbk.entrySet(); Iterator<Map.Entry<String, HashMap<String, String>>> classNameIt = classNameSet.iterator(); while (classNameIt.hasNext()) { Map.Entry<String, HashMap<String, String>> classNameEntry = classNameIt.next(); String classNameKey = classNameEntry.getKey(); HashMap<String, String> classMap = classNameEntry.getValue(); Set<Map.Entry<String, String>> studentSet = classMap.entrySet(); Iterator<Map.Entry<String, String>> studentIt = studentSet.iterator(); while (studentIt.hasNext()) { Map.Entry<String, String> studentEntry = studentIt.next(); String numKey = studentEntry.getKey(); String nameValue = studentEntry.getValue(); System.out.println(classNameKey + "..." + numKey + "..." + nameValue); } } } public static void keySet(HashMap<String, HashMap<String, String>> czbk) { Set<String> classNameSet = czbk.keySet(); Iterator<String> classNameIt = classNameSet.iterator(); while (classNameIt.hasNext()) { String classNameKey = classNameIt.next(); HashMap<String, String> classMap = czbk.get(classNameKey); Set<String> studentNum = classMap.keySet(); Iterator<String> studentIt = studentNum.iterator(); while (studentIt.hasNext()) { String numKey = studentIt.next(); String nameValue = classMap.get(numKey); System.out.println(classNameKey + "..." + numKey + "..." + nameValue); } } } }========================================Talk is cheap, show me the code=======================================