Java集合类知识点总结

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Vector;

public class ListTest {
	public static void main(String[] args){
		List arrayList=new ArrayList();
		List linkedList=new LinkedList();
		List vector=new Vector();
		
		arrayList.add("1"); //字符类型
		arrayList.add("1"); //重复元素
		arrayList.add("2");
		arrayList.add(1); //数字类型
		
		linkedList.add("1");
		linkedList.add("1");
		linkedList.add("2");
		linkedList.add(1);
		
		vector.add("1");
		vector.add("1");
		vector.add("2");
		vector.add(1);
		
		for(Object obj:arrayList){ //foreach循环
			System.out.println(obj);
		}
		
		for(int i=0;i<linkedList.size();i++){ //普通for循环
			System.out.println(arrayList.get(i));
		}
		
		Iterator it = vector.iterator(); //迭代器
		while(it.hasNext()){
			Object j=it.next();
			System.out.println(j);
		}
	}
}

public class SetTest {
	public static void main(String[] args){
		Set hashSet=new HashSet();
		Set treeSet=new TreeSet();
		
		hashSet.add("1"); //字符类型
		hashSet.add("1"); //重复元素
		hashSet.add("2");
		hashSet.add(1); //数字类型
		
		treeSet.add("1");
		treeSet.add("1");
		treeSet.add("2");
//		treeSet.add(1); //报错，treeSet不能添加不同的数据类型
		
		for(Object i:hashSet){ //foreach循环
			System.out.println(i);
		}
		
		Iterator it = treeSet.iterator(); //迭代器
		while(it.hasNext()){
			Object j=it.next();
			System.out.println(j);
		}
	}
}

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

public class MapTest {
	public static void main(String[] args){
		Map hashMap=new HashMap();
		Map hashtable=new Hashtable();
		Map treeMap=new TreeMap();
		
		hashMap.put(1, "1"); //字符类型值
		hashMap.put(2, "1"); //同值不同键
		hashMap.put(3, "2");
		hashMap.put(4, 1); //数字类型值
		hashMap.put("5", 1); //字符类型键
		
		hashtable.put(1, "1");
		hashtable.put(2, "1");
		hashtable.put(3, "2");
		hashtable.put(4, 1);
		hashtable.put("5", 1);
		
		treeMap.put(1, "1");
		treeMap.put(2, "1");
		treeMap.put(5, "2");
		treeMap.put(4, 1);
//		treeMap.put("5", 1); //报错，TreeMap不能添加不同类型的键
		
		//遍历hashMap键
		for(Object key:hashMap.keySet()){
			System.out.println(key);
		}
		//遍历hashtable值
		for(Object value:hashtable.values()){
			System.out.println(value);
		}

		//遍历hashMap键值对
		Set set = hashMap.keySet();
		for(Iterator iter = set.iterator(); iter.hasNext();){
			Object key = iter.next();
			Object value = hashMap.get(key);
			System.out.println(key+"\t"+value);
		}
		
		//迭代遍历hashtable键值对,倒序！
		Iterator table = hashtable.entrySet().iterator();
		while(table.hasNext()){
			Map.Entry entry = (Map.Entry) table.next(); 
			Object key = entry.getKey(); //取键
			Object value = entry.getValue(); //取值
			System.out.println(key+"\t"+value); 
		}
		
		//迭代遍历treeMap键值对
		Iterator tmp = treeMap.entrySet().iterator();
		while(tmp.hasNext()){
			Map.Entry entry = (Map.Entry) tmp.next(); 
			Object key = entry.getKey(); //取键
			Object value = entry.getValue(); //取值
			System.out.println(key+"\t"+value); 
			
		}
	}
}