diff --git a/src/chapter6/Example14.java b/src/chapter6/Example14.java index 6885386..1a2fb3e 100644 --- a/src/chapter6/Example14.java +++ b/src/chapter6/Example14.java @@ -1,4 +1,27 @@ package chapter6; +import java.util.HashMap; + public class Example14 { + public static void main(String[] args) { + HashMap map = new HashMap(); // 创建Map对象 + map.put("1","张三");//存储键和值 + map.put("2","李四"); + map.put("3","王五"); + map.put("3", "赵六"); + + System.out.println("1:" + map.get("1")); // 根据键获取值 + System.out.println("2: " + map.get("2")); + System.out.println("3: " + map.get("3")); + System.out.println("键值对数量:" + map.size()); + +// if (map.containsKey("1")) { +// System.out.println("1号存在"); +// } +// +// if (map.containsValue("李四")) { +// System.out.println("李四存在"); +// } + + } } diff --git a/src/chapter6/Example15.java b/src/chapter6/Example15.java index 68c18fd..2ab7d09 100644 --- a/src/chapter6/Example15.java +++ b/src/chapter6/Example15.java @@ -1,4 +1,52 @@ package chapter6; +import java.util.HashMap; +import java.util.Iterator; +import java.util.Map; +import java.util.Set; + public class Example15 { + public static void main(String[] args) { + HashMap map = new HashMap(); // 创建Map对象 + map.put("2","李四"); //存储键和值 + map.put("3","王五"); + map.put("1","张三"); + + // 方法一 + Set keySet = map.keySet(); //获取键的集合 + Iterator it = keySet.iterator();//选代键的集合 + while (it.hasNext()) { + Object key = it.next(); + Object value = map.get(key); //获取每个键所对应的值 + System.out.println(key + ":" + value); + } + + Iterator it2 = map.keySet().iterator(); + while (it2.hasNext()) { + Object key = it2.next(); + System.out.println(key); + } + + Iterator it3 = map.values().iterator(); + while (it3.hasNext()) { + Object value = it3.next(); + System.out.println(value); + } + + // 方法二 + Set entrySet = map.entrySet(); // 获取所有映射关系 + Iterator it4 = entrySet.iterator(); // 获取Iterator对象 + while (it4.hasNext()){ + //获取集合中键值对映射关系 + Map.Entry entry = (Map.Entry) (it4.next()); + Object key = entry.getKey();//获取Entry中的键 + Object value = entry.getValue();//获取Entry中的值 + System.out.println(key + ":" + value); + } + + for (Object obj : map.entrySet()) { + System.out.println(obj); + } + + } } diff --git a/src/chapter6/Example19.java b/src/chapter6/Example19.java index 34bb4c6..e0aad69 100644 --- a/src/chapter6/Example19.java +++ b/src/chapter6/Example19.java @@ -1,4 +1,23 @@ package chapter6; +import java.util.Iterator; +import java.util.Set; +import java.util.TreeMap; + public class Example19 { + public static void main(String[] args) { + TreeMap map = new TreeMap(); // 创建Map集合 + map.put(3, "李四"); // 存储键和值 + map.put(2, "王五"); + map.put(4, "赵六"); + map.put(3, "张三"); + + Set keySet = map.keySet(); + Iterator iterator = keySet.iterator(); + while (iterator.hasNext()) { + Object key = iterator.next(); + Object value = map.get(key); + System.out.println(key + ":" + value); + } + } }