Detailed explanation of collection class methods____ （4） Judgment and assignment, etc

1、disjoint(Collection<?> c1,Collection<?> c2);

        Compare sets c1 And collection c2 There are no common elements between them , Go back when you have true, Instead, return to false

public class CollectionsDome3 {
    public static void main(String[] args) {
        ArrayList<Integer> c1 = new ArrayList<Integer>(Arrays.asList(2,4,6,8,9,6));
        ArrayList<Integer> c2 = new ArrayList<Integer>(Arrays.asList(1));
        boolean flge = Collections.disjoint(c1 , c2);
        System.out.println(flge);  // The output is true
    }
}

2、addAll(Collection<? super T> c,T...a)

                      Add the specified collection to the collection c in ,T...a Represents a variable parameter ,a Array equivalent

public class CollectionsDome3 {
    public static void main(String[] args) {
        ArrayList<Integer> c1 = new ArrayList<Integer>(Arrays.asList(2,4,6,8,9,6));
        Collections.addAll(c1,2,3,5,7,8,9);
        System.out.println(c1);
    }
}

3、copy(List  m,List  n)

          take n The element in is assigned to m in .

public class CollectionsDome3 {
    public static void main(String[] args) {
        ArrayList<Integer> c1 = new ArrayList<Integer>(Arrays.asList(2,4,6,8,9,6));
        ArrayList<Integer> c2 = new ArrayList<Integer>(Arrays.asList(1));
        Collections.copy(c1,c2);// take c2 The value of is assigned to c1, Cover from beginning to end    c2.size()<=c1.size()
        System.out.println(c1);//[1, 4, 6, 8, 9, 6]
        System.out.println(c2);//[1]
    }
}

4、checkedXxx()

          Check if this collection is Xxx Collection types .

      for example ：   checkedCollection(Collection   c,class   o.class)

           c、 Represents a collection for which type safe views are obtained at run time .o、 Represents the element types that a given collection is allowed to store .

This command is used to return the specified set Dynamic security view

        The following other methods are created in the same way as this

public class CollectionsDome3 {
    public static void main(String[] args) {
        Collection c3=new ArrayList();
         c3.add(1);
         c3.add("df");
        Collection<Student> strings =  Collections.checkedCollection(c3 ,Integer.class);
         c3.add("dddd");
        System.out.println(c3);//[1, df, dddd] 
        System.out.println(strings);//[1, df, dddd]  strings The set cannot be changed 
    }
}

checked	explain
checkedList(List   c,class   o.class)	List aggregate , Return to dynamic security view
checkedMap(Mapn   c,class   o.class)	Map aggregate , Return to dynamic security view
checkedNavigableMap(NavigableMap  c,class   o.class)	NavigableMap aggregate , Return to dynamic security view
checkedNavigableSet(NavigableSet   c,class   o.class)	NavigableSet aggregate , Return to dynamic security view
checkedQueue(Queue  c,class   o.class)	Queue aggregate , Return to dynamic security view
checkedSet(Set   c,class   o.class)	Set aggregate , Return to dynamic security view
checkedSortedMap(SortedMap  c,class   o.class)	SortedMap aggregate , Return to dynamic security view
checkedSortedSet(SortedSet   c,class   o.class)	SortedSet aggregate , Return to dynamic security view

5、asLifoQueue(Deque    deque);

                 Double ended queue （ fifo , The queue is full , Then the first segment has priority to exit ） Expressed as Lifo queue （LIFO Last in first out ）

          

public class CollectionsDome3 {
    public static void main(String[] args) {
        Deque<Integer> queue=new ArrayDeque<Integer>();// deque , fifo 
        queue.add(1);queue.add(2);
        System.out.println(queue);// Output [1,2]
//        Deque convert to Queue queue 
        Queue<Integer> i = Collections.asLifoQueue(queue);//Lifo queue , First in, then out 
        System.out.println(i);

    }
}

6、list(Enumeration  en);

             Returns an array , This list contains the given Enumeration ( enumeration ) All elements returned , And store these elements in the order returned by enumeration ArrayList The method in .

package cn.cm;

import java.util.*;

public class Peal {
    public static void main(String args[]) {
        // Instantiate an ArrayList and
        // Stack object
        List arr_l = new ArrayList();
        Stack st = new Stack();// Stack queue , Last in, first out 
        // By using push() method is
        // to add elements in stack
        st.push(10);// Store elements 
        st.push(20);
        st.push(30);
        st.push(40);
        st.push(50);
        System.out.println(st.pop());// Output 50, Take out this element , There is no such element in the collection 
        System.out.println(st.pop());// Output 40, Take out this element , There is no such element in the collection 
        System.out.println(st.pop());// Output 30, Take out this element , There is no such element in the collection 
        System.out.println(st);//st Only left in the set 【10,20】
        // Get elements in an enumeration object
        Enumeration en = st.elements();//  Create an enum type object 
        System.out.println(en.nextElement());// take out 1 Elements 10
        // By using list() method is to
        // return the array list of the
        // given enumeration object
        ArrayList arr_1 = Collections.list(en);//  take en The return element of enumerating the remaining elements exists arr_1 in 
                                                 // only [20]
        System.out.println("Collections.list(en): " + arr_1);// Output [20]
    }
}

7、singleton(),singletonMap()、singletonList()  

          These are single column modes , There's only one element .

      adopt Collection.singleton(sc) Create a single column schema element , In turn, is Set type ,Map type ,List type .

public class Sidjsn extends Student {
    public static void main(String[] args) {
        List sc=new ArrayList(Arrays.asList(1,2,4,5));
        List sc1=new ArrayList(Arrays.asList(1,2,4,6));
        Set<List> s = Collections.singleton(sc);
        System.out.println(s); // [[1, 2, 4, 5]]
//        s.add(sc);    I can't ,s Just a singleton mode , There can only be one element 
        
        List<List> s1 = Collections.singletonList(sc);
        System.out.println(s1);// [[1, 2, 4, 5]]
        
        Map<Integer, List> s2 = Collections.singletonMap(1 , sc);
        System.out.println(s2);//        System.out.println(s2);//
        System.out.println(sc);  // [1, 2, 4, 5]
    }
}