Java里的list,set,map操作方法
来源 :中华考试网 2020-10-28
中//ArrayList
{
ArrayList arraylist=new ArrayList();
arraylist.add(0,"end");//指定索引加入值
//需注意的是,如果现有2个值,我加入索引为5的那么就会出现异常
for(int i=0;i<2;i++){
arraylist.add(i,String.valueOf(i));
}
System.out.println("ArrayList:");
for(int i=0;i System.out.print(arraylist.get(i)+";"); } arraylist.add("0");//直接加入值到ArrayList的最后 arraylist.add("0"); System.out.print("\nArrayList\'s lastIndexOf(\"0\") is "+arraylist.lastIndexOf("0")); } //Arrays { String []array=new String[]{"a","b","c"}; List list=Arrays.asList(array); System.out.println("\nArrays:"); for(int i=0;i System.out.print(list.get(i)+";"); } System.out.print("\nArrays\'s length is "+array.length);//打印数组的长度 } //Collections { String []array=new String[]{"a","b","c"}; List list=Arrays.asList(array); Collections.fill(list,"Fill");//用Fill填充全部元素 System.out.println("\nCollections:"); for(int i=0;i System.out.print(list.get(i)+";"); } array=new String[]{"1","2","3"}; List list2=Arrays.asList(array); Collections.copy(list,list2);//拷贝list2的数据进list System.out.println("\n"+list); Collections.swap(list,2,1);//调换索引为1和2的元素的位置 System.out.println(list); } //EventObject { String s="hello"; String s2=s; EventObject eventobject=new EventObject(s);//一个准容器类型,确切的归类它不是容器 System.out.println("EventObject:"); System.out.println(eventobject.getSource()); System.out.println(eventobject.equals(s2)); } //HashMap { HashMap hashmap=new HashMap();//一个速度最快的容器 hashmap.put("0","c"); hashmap.put("1","a"); hashmap.put("2","b"); hashmap.put("3","a"); System.out.println("HashMap:"); System.out.println(hashmap);//该容器有其内部的排序方式 Set set=hashmap.keySet();//获取全部键 Iterator iterator=set.iterator(); while(iterator.hasNext()){ System.out.print(hashmap.get(iterator.next())+";"); } } //HashSet { HashSet hashset=new HashSet();//一个绝对不能重复的类型 hashset.add("c"); hashset.add("b"); hashset.add("a"); hashset.add("a"); hashset.add("b"); System.out.println("\nHashSet:"); System.out.println(hashset); Iterator iterator=hashset.iterator();//取出元素 while(iterator.hasNext()){ System.out.print(iterator.next()+";"); } } //Hashtable { Hashtable hashtable=new Hashtable();//一个完全可以由其他容器替换的老容器类型 hashtable.put("0","c"); hashtable.put("1","a"); hashtable.put("3","c"); hashtable.put("2","b"); System.out.println("\nHashtable:"); Enumeration enumeration=hashtable.elements();//获取元素,Enumeration已经不是主流,Iterator是它的下一代替代品 while(enumeration.hasMoreElements()){ System.out.print(enumeration.nextElement()+";"); } } //IdentityHashMap { IdentityHashMap identityhashmap=new IdentityHashMap(); identityhashmap.put("0","c"); identityhashmap.put("1","a"); identityhashmap.put("3","b"); identityhashmap.put("2","a"); System.out.println("\nIdentityHashMap:"); System.out.println(identityhashmap); System.out.println(identityhashmap.containsKey("3"));//是否包含这个键 System.out.println(identityhashmap.containsValue("a"));//是否包含值 Set set=identityhashmap.entrySet();//传为Set类型 System.out.println(set); set=identityhashmap.keySet();//全部键 System.out.println(set); } //LinkedHashMap { LinkedHashMap linkedhashmap=new LinkedHashMap(); linkedhashmap.put("0","b"); linkedhashmap.put("2","a"); linkedhashmap.put("1","c"); linkedhashmap.put("3","b"); System.out.println("LinkedHashMap:"); System.out.println(linkedhashmap); System.out.println(linkedhashmap.containsKey("2"));//是否包含这个键 System.out.println(linkedhashmap.containsValue("c"));//是否包含值 Set set=linkedhashmap.keySet(); Iterator iterator=set.iterator(); while(iterator.hasNext()){ System.out.print(linkedhashmap.get(iterator.next())+";"); } } //LinkedHashSet { LinkedHashSet linkedhashset=new LinkedHashSet();//它包含了几种Set的属性但却没有自己的特色 linkedhashset.add("c"); linkedhashset.add("a"); linkedhashset.add("a"); linkedhashset.add("b"); System.out.println("\nLinkedHashSet:"); System.out.println(linkedhashset); System.out.println(linkedhashset.contains("a"));//是否包含对象 Iterator iterator=linkedhashset.iterator(); while(iterator.hasNext()){ System.out.print(iterator.next()+";"); } } //LinkedList { LinkedList linkedlist=new LinkedList();//自由使用是它的特色 linkedlist.add("a"); linkedlist.add(1,"c"); linkedlist.addLast("b"); linkedlist.addFirst("d"); System.out.println("\nLinkedList:"); System.out.println(linkedlist); //linkedlist.clear();//该方法清空容器 //linkedlist.remove(0);//删除索引为0的元素 //linkedlist.remove("d");//删除值为d的元素 //linkedlist.removeFirst();//删除第一个元素 //linkedlist.removeLast();//删除最后一个元素 for(int i=0;i System.out.print(linkedlist.get(i)+";"); } } //Stack { Stack stack=new Stack();//堆栈 stack.add("b"); stack.add(0,"c"); stack.push("d"); stack.add("e"); stack.push("a"); Enumeration enumeration=stack.elements(); System.out.println("\nStack:"); while(enumeration.hasMoreElements()){ System.out.print(enumeration.nextElement()+";"); } //后进先出 System.out.println("\n"+stack.peek()); System.out.println(stack.pop()); System.out.println(stack.contains("d")+";"+stack.contains("a"));//是否包含该元素,有趣的事情发生了 System.out.println(stack.search("c"));//非常有用的属性,检索,但是由后向前的排列 } //TreeMap { TreeMap treemap=new TreeMap(); treemap.put("0","d"); treemap.put("2","a"); treemap.put("1","b"); treemap.put("3","c"); System.out.println("\nTreeMap:");//可以对键排序 System.out.println(treemap); System.out.println(treemap.firstKey());//返回第一个键 Set set=treemap.keySet(); Iterator iterator=set.iterator(); while(iterator.hasNext()){ System.out.print(treemap.get(iterator.next())+";"); } } //TreeSet { TreeSet treeset=new TreeSet();//自动排序内容 treeset.add("b"); treeset.add("a"); treeset.add("c"); treeset.add("d"); System.out.println("\nTreeSet:"); System.out.println(treeset); System.out.println(treeset.first());//返回第一个元素 Iterator iterator=treeset.iterator(); while(iterator.hasNext()){ System.out.print(iterator.next()+";"); } } //Vector { Vector vector=new Vector(); vector.add(0,"b"); vector.add("a"); vector.addElement("d"); vector.add("c"); System.out.println("\nVector:"); System.out.println(vector); vector.set(2,"h");//替换掉指定索引的元素 System.out.println(vector); Object []str=vector.toArray(); for(int i=0;i System.out.print(str[i]+";"); } vector.setSize(2);//重新设置大小为2 System.out.println("\n"+vector); } //WeakHashMap { WeakHashMap weakhashmap=new WeakHashMap(); weakhashmap.put("1","b"); weakhashmap.put("2","c"); weakhashmap.put("0","d"); weakhashmap.put("3","a"); System.out.println("\nWeakHashMap:"); System.out.println(weakhashmap); System.out.println(weakhashmap.containsKey("3"));//是否包含键 System.out.println(weakhashmap.containsValue("d"));//是否包含值 Set set=weakhashmap.entrySet(); Iterator iterator=set.iterator(); while(iterator.hasNext()){ System.out.print(iterator.next()+";"); } //weakhashmap.remove("2");//删除该键对应的值 //weakhashmap.get("1");//获取指定键的值 } }