java 9999

Posted 2020-11-19 ftl1012

1. map

1.1. map中的方法

1.2. Map.Entry

对于集合来讲，就是把kye-value的数据保存在了Map.Entry的实例之后，再在Map集合中插入了一个Map.Entry的实例化对象

Map.Entry一般用于输出集合

1.3. Map接口的常用子类

1.4. HashTable和HashMap区别

1.5. Map的标准输出(2个)

方案一：

方案二：

1.6. 人员配置

package com.ftl;

import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.TreeMap;

public class Test2018 {
	public static void main(String[] args) {

		Map<String, String> map = new TreeMap<>();
		map.put("Hello", "world");
		map.put("Hello1", "world1");
		map.put("Hello2", "world2");
		map.put("Hello3", "world3");
		String str = map.get("Hello");
		Set<String> set = map.keySet();
		Collection<String> values = map.values();
		Iterator<String> iterator = set.iterator();
		Iterator<String> iter = values.iterator();
		System.out.println("
foreach方法：");
		for (String s : values) {
			System.out.print(s + "、");
		}
		System.out.println("
Iterator方法：");
		while (iterator.hasNext()) {
			System.out.print(iterator.next() + "、");
		}
		System.out.println("
Map的标准输出_1(Map.entrySet)：");
		Set<Entry<String, String>> entrySet = map.entrySet();
		Iterator<Map.Entry<String, String>> it = entrySet.iterator();
		while (it.hasNext()) {
			Map.Entry<String, String> next = it.next();
			System.out.print(next.getKey() + "-->: " + next.getValue() + "
");
		}
		System.out.println("
Map的标准输出_2(Foreach)：");
		for (Map.Entry<String, String> entry : entrySet) {
			System.out.print(entry.getKey() + "-->: " + entry.getValue() + "
");
		}
		System.out.println("Map.entrySet()大小：" + map.entrySet().size());
	}
}