java ArrayList exercises

Package java06;
 / * 
* 6 1--33 randomly generated number, and stores the list, and then traversing 
* * / 

Import of java.util.ArrayList;
 Import java.util.Random; 

public  class Demolianxi {
     public  static  void {main (String [] args) 
        the Random R & lt = new new the Random (); 
        the ArrayList List = <Integer> new new the ArrayList <> ();
         for ( int I = 0; I <. 6; I ++ ) {
             int NUM = r.nextInt ( 33 is) + 1'd ; 
            List.add (NUM); 
        }
        System.out.println(list);
        System.out.println("========");
        for (int i = 0; i < list.size(); i++) {
            System.out.print(list.get(i)+ " ");

        }
    }
}

Package Penalty for java06; 

Import java.util.ArrayList; 

/ * 
Title: a custom class, add to the collection, and iterate 

ideas: 
1, the definition of a student from class, four parts 
2, create a collection, storage hard student objects, pan type <student> 
. 3, according to the class, to create four students objects 
4, adds four students object to the collection the Add 
. 5, through the collection: for size GET 
* * / 
public  class DemoArrayListStudent {
     public  static  void main (String [] args ) { 
        the ArrayList <Student> List = new new the ArrayList <> (); 
        Student One = new new Student ( "melon", 21 is ); 
        Student TWO = new new Student ( "watermelon", 22);
        Student three = new Student("南瓜",23);
        Student four = new Student("杯瓜",24);

        list.add(one);
        list.add(three);
        list.add(two);
        list.add(four);
        System.out.println(list);//[java06.Student@282ba1e, java06.Student@13b6d03, java06.Student@f5f2bb7, java06.Student@73035e27]
        System.out.println("====================");

        for (int i = 0; i < list.size(); i++) {
            Student stu = list.get(i);
            System.out.println("Name:" + stu.getName () + " , the age" + stu.getAge ());
             / * 
            * Name: melon, age 21 
　　　　　　　　Name: pumpkin, age 23 
　　　　　　　　Name: watermelon, age 22 
　　　　　　　　Name: cup melon, age 24 * / 

        } 
    } 
} 

// Create student class 
Package java06; 

public  class student {
     Private String name;
     Private   int Age; 

    public student () { 
    } 

    public student (String name, int Age) {
         the this .name = name;
         the this . = Age Age; 
    } 

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

Package java06;
 / * 
Title: 
define a set format to specify a method of printing (the ArrayList type as a parameter), except that {} from a set of spreading, using @ dividing each element 

System.out.pritln (list) [10,20,30] 
printArrayList (List) @ 20 is 10 {30} @ 
* * / 

Import of java.util.ArrayList; 

public  class DemoArrayListPrint {
     public  static  void main (String [] args) { 
        the ArrayList <Integer> = List new new the ArrayList <> (); 
        List .add ( 10 ); 
        List.add ( 20 is ); 
        List.add ( 30 ); 
        System.out.println (List);
        printArrayList (List); 
    } 

    / * 
    Method three elements: 
    1. Return Value Type: This example knowledge printing, no operation, no results, so use void 
    2, Method name: printArratList 
    . 3, the parameter list List 
    * * / 
        public  static  void printArrayList (the ArrayList List) { 
            of System.out.print ( "{" );
             for ( int I = 0; I <list.size (); I ++ ) { 
                of System.out.print (List.get (I)); 
                IF (I list.size == () -. 1 ) { 
                    System.out.println ( "}" ); 
                } the else { 
                    of System.out.print ( "@" );
                }

            }
        }

    }

Package java06;
 / * 
Title: 
with a large collection of random numbers is stored in 20, wherein the screening elements of even-numbered years and then, into which a small set of 
requirements: the method implemented by custom 

* * / 

Import of java.util.ArrayList;
 Import java.util.Random; 

public  class DemoArrayListReturn {
     public  static  void main (String [] args) { 
        the Random R & lt = new new the Random (); 
        the ArrayList <Integer> = List new new the ArrayList <> ();
         for ( int I = 0; I <20 is; I ++ ) {
             int NUM = r.nextInt (100) + 1'd ;
            list.add(num);
        }
        ArrayList<Integer> smallList = douNumList(list);
        System.out.println(smallList);
        for (int i = 0; i <smallList.size(); i++) {
            System.out.println(smallList.get(i));

        }
        
    }
    public static ArrayList<Integer> douNumList(ArrayList<Integer> list){
        ArrayList<Integer> list2 = new ArrayList<>();
        for (int i = 0; i < list.size(); i++) {
            int num = list.get(i);
            if (num%2==0){
                list2.add(num);
            }

        }
        return list2;
    }
}