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Java里的list,set,map操作方法

来源 :中华考试网 2020-10-28

  //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

  }

  }

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