Java入门

此文转载自：https://blog.csdn.net/qq_44799830/article/details/111767642#commentBox

一、多态

1.Abstract_Music.java（抽象）

enum Note1{
    Low,Middle,High
}
abstract class Instrument1{
    abstract void play(Note n);
    abstract void adjust();
}
class Wind1 extends Instrument1{
    void play(Note n){System.out.println("Wind1 play()");}
    void adjust(){System.out.println("Wind1 adjust()");}
}
class Percussion1 extends Instrument1{
    void play(Note n){System.out.println("Percussion1 play()");}
    void adjust(){System.out.println("Percussion1 adjust()");}
}
class Stringed1 extends Instrument1{
    void play(Note n){System.out.println("Stringed1 play()");}
    void adjust(){System.out.println("Stringed1 adjust()");}
}
class Brass1 extends Instrument1{
    void play(Note n){System.out.println("Brass1 play()");}
    void adjust(){System.out.println("Brass1 adjust()");}
}
class Woodwind1 extends Instrument1{
    void play(Note n){System.out.println("Woodwind1 play()");}
    void adjust(){System.out.println("Woodwind1 adjust()");}
}

public class Abstract_Music {
    public static void tune(Instrument1 i){i.play(Note.Low);}
    public static void tuneall(Instrument1[] e){
        for(Instrument1 i:e)
            tune(i);
    }
    public static void main(String[] args){
        System.out.println("===========single orchestra===========");
        Instrument1 orchestra4=new Brass1();
        orchestra4.adjust();
        System.out.println("===========many orchestra===========");
        Instrument1[] orchestra3={new Woodwind1(),new Stringed1(),new Wind1(),new Percussion1()};
        Abstract_Music m=new Abstract_Music();
        m.tuneall(orchestra3);
}
}

 run:
===========single orchestra===========
Brass1 adjust()
===========many orchestra===========
Woodwind1 play()
Stringed1 play()
Wind1 play()
Percussion1 play()
BUILD SUCCESSFUL (total time: 0 seconds)

2.Interface_Music.java（接口）

enum Note2{
    Low,Middle,High
}
interface Instrument2{
    void play(Note n);
    void adjust();
}
class Wind2 implements Instrument2{
    public void play(Note n){System.out.println("Wind2 play()"+n);}
    public void adjust(){System.out.println("Wind2 adjust()");}
}
class Percussion2 implements Instrument2{
    public void play(Note n){System.out.println("Percussion2 play()"+n);}
    public void adjust(){System.out.println("Percussion2 adjust()");}
}
class Stringed2 implements Instrument2{
    public void play(Note n){System.out.println("Stringed2 play()"+n);}
    public void adjust(){System.out.println("Stringed2 adjust()");}
}
class Brass2 implements Instrument2{
    public void play(Note n){System.out.println("Brass2 play()"+n);}
    public void adjust(){System.out.println("Brass2 adjust()");}
}
class Woodwind2 implements Instrument2{
    public void play(Note n){System.out.println("Woodwind2 play()"+n);}
    public void adjust(){System.out.println("Woodwind2 adjust()");}
}

public class Interface_Music {
    public static void tune(Instrument2 i){i.play(Note.High);}
    public static void tuneall(Instrument2[] e){
        for(Instrument2 i:e)
            tune(i);
    }
    public static void main(String[] args){
        System.out.println("===========single orchestra===========");
        Instrument2 orchestra7=new Brass2();
        orchestra7.adjust();
        System.out.println("===========many orchestra===========");
        Instrument2[] orchestra8={new Woodwind2(),new Stringed2(),new Wind2(),new Percussion2()};
        Interface_Music n=new Interface_Music();
        n.tune(orchestra7);
        n.tuneall(orchestra8);
}
}

 run:
===========single orchestra===========
Brass2 adjust()
===========many orchestra===========
Brass2 play()High
Woodwind2 play()High
Stringed2 play()High
Wind2 play()High
Percussion2 play()High
BUILD SUCCESSFUL (total time: 0 seconds)

 3.Music.java（继承）

enum Note{
    Low,Middle,High
}
class Instrument{
    void play(Note n){System.out.println("Instrument play()");}
    void adjust(){System.out.println("Instrument adjust()");}
}
class Wind extends Instrument{
    void play(Note n){System.out.println("Wind play()");}
    void adjust(){System.out.println("Wind adjust()");}
}
class Percussion extends Instrument{
    void play(Note n){System.out.println("Percussion play()");}
    void adjust(){System.out.println("Percussion adjust()");}
}
class Stringed extends Instrument{
    void play(Note n){System.out.println("Stringed play()");}
    void adjust(){System.out.println("Stringed adjust()");}
}
class Brass extends Instrument{
    void play(Note n){System.out.println("Brass play()");}
    void adjust(){System.out.println("Brass adjust()");}
}
class Woodwind extends Instrument{
    void play(Note n){System.out.println("Woodwind play()");}
    void adjust(){System.out.println("Woodwind adjust()");}
}

public class Music {
    public static void tune(Instrument i){i.play(Note.Low);}
    public static void tuneall(Instrument[] e){
        for(Instrument i:e)
            tune(i);
    }
    public static void main(String[] args){
        System.out.println("==========orchestra============");
        Instrument orchestra=new Brass();
        orchestra.adjust();
        System.out.println("===========orchestra1===========");
        Instrument[] orchestra1={new Instrument(),new Woodwind(),new Stringed(),new Wind(),new Percussion()};
        Music m=new Music();
        m.tuneall(orchestra1);
    }
}

 run:
==========orchestra============
Brass adjust()
===========orchestra1===========
Instrument play()
Woodwind play()
Stringed play()
Wind play()
Percussion play()
BUILD SUCCESSFUL (total time: 0 seconds)

二、多重继承

1.Adventure.java

interface CanFight{
    void fight();
}
interface CanSwim{
    void swim();
}
interface CanFly{
    void fly();
}
class AcionCharacter{
    public void fight(){System.out.println("AcionCharacter can fight.");}
}
class Hero extends AcionCharacter implements CanFight,CanSwim,CanFly{

    @Override
    public void swim() {
        System.out.println("Hero AcionCharacter can swim.");
    }

    @Override
    public void fly() {
        System.out.println("Hero AcionCharacter can fly.");
    }  
}
public class Adventure {
    public static void t(CanFight x){x.fight();}
    public static void u(CanSwim x){x.swim();}
    public static void v(CanFly x){x.fly();}
    public static void w(AcionCharacter x){x.fight();}
    public static void main(String[] args){
        Hero h=new Hero();
        t(h);
        u(h);
        v(h);
        w(h);
    }
}

 run:
AcionCharacter can fight.
Hero AcionCharacter can swim.
Hero AcionCharacter can fly.
AcionCharacter can fight.
BUILD SUCCESSFUL (total time: 0 seconds)

2.HorrorShow.java

interface Monster{
    void menace();
}
interface DangerousMonster extends Monster{
    void destroy();
}
interface Lethal{
    void kill();
}
interface Vampire extends DangerousMonster,Lethal{
    void drinkblood();
}
class BadVampire implements Vampire{

    @Override
    public void drinkblood() {
        System.out.println("BadVampire can menace.");
    }

    @Override
    public void destroy() {
        System.out.println("BadVampire can menace.");
    }

    @Override
    public void menace() {
        System.out.println("BadVampire can menace.");
    }

    @Override
    public void kill() {
        System.out.println("BadVampire can menace.");
    }   
}
class Dragon implements DangerousMonster{

    @Override
    public void destroy() {
        System.out.println("Dragon can destroy.");
    }

    @Override
    public void menace() {
        System.out.println("Dragon can menace.");
    }
    
}
public class HorroShow {
    static void u(Monster x){x.menace();}
    static void v(DangerousMonster x){
        x.menace();
        x.destroy();
    }
    static void w(Lethal x){x.kill();}
    public static void main(String[] args){
        DangerousMonster barney=new Dragon();
        u(barney);
        v(barney);
        Vampire vlad=new BadVampire();
        u(vlad);
        v(vlad);
        w(vlad);
    }
}

 run:
Dragon can menace.
Dragon can menace.
Dragon can destroy.
BadVampire can menace.
BadVampire can menace.
BadVampire can menace.
BadVampire can menace.
BUILD SUCCESSFUL (total time: 0 seconds)

三、适配接口

1.Randomdoubles.java

import java.util.*;
public class Randomdoubles {
    private static Random rand=new Random(47);
    public double next(){return rand.nextDouble();}
    public static void main(String[] args){
        Randomdoubles rd=new Randomdoubles();
        for(int i=0;i<7;i++){
            System.out.println(rd.next()+"  ");
        }
    }
}

 run:
0.7271157860730044  
0.5309454508634242  
0.16020656493302599  
0.18847866977771732  
0.5166020801268457  
0.2678662084200585  
0.2613610344283964  
BUILD SUCCESSFUL (total time: 0 seconds)

2.Randomwords.java

import java.io.IOException;
import java.nio.*;
import java.util.*;
public class Randomwords implements Readable{
    private static Random rand=new Random(47);
    private static final char[] capitals="ABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
    private static final char[] lowers="abcdefghijklmnopqrstuvwxyz".toCharArray();
    private static final char[] vowels="aeiou".toCharArray();
    private int count;
    public Randomwords(int count){this.count=count;}
    @Override
    public int read(CharBuffer cb) throws IOException {
        if(count--==0){ return -1;}
        cb.append(capitals[rand.nextInt(capitals.length)]);
        for(int i=0;i<4;i++){
            cb.append(lowers[rand.nextInt(lowers.length)]);
            cb.append(vowels[rand.nextInt(vowels.length)]);
        }
        cb.append(" ");
        return 10;
    }
    public static void main(String[] args){
        Scanner s=new Scanner(new Randomwords(10));
        while(s.hasNext()){
            System.out.println(s.next());
        }
    }
}

 run:
Ynobenogi
Foozutoqe
Gsegemuje
Roisueeue
Neueolome
Hlieehoca
Reeuebiki
Naieobuwa
Kjirokope
Wsupodoco
BUILD SUCCESSFUL (total time: 0 seconds)

3.AdaptedRandomDoubles.java

import java.io.IOException;
import java.nio.*;
import java.util.*;
public class AdaptedRandomDoubles extends Randomdoubles implements Readable{ 
    private int count;
    public AdaptedRandomDoubles(int count){this.count=count;}
    @Override
    public int read(CharBuffer cb) throws IOException {
        if(count--==0){ return -1;}
        String result=Double.toString(next())+" ";
        cb.append(result);
        return cb.length();
    }
    public static void main(String[] args){
        Scanner s=new Scanner(new AdaptedRandomDoubles(7));
        while(s.hasNext()){
            System.out.println(s.nextDouble()+"  ");
        }
    }
}

 run:
0.7271157860730044  
0.5309454508634242  
0.16020656493302599  
0.18847866977771732  
0.5166020801268457  
0.2678662084200585  
0.2613610344283964  
BUILD SUCCESSFUL (total time: 0 seconds)

四、嵌套接口

1.Factories.java

interface Service{
    void method1();
    void method2();
}
interface Servicefactories{
    Service getservice();
}
class Implemention1 implements Service{
    public void method1(){System.out.println("Implemention1 method1");}
    public void method2(){System.out.println("Implemention1 method2");}
}
class Implemention2 implements Service{
    public void method1(){System.out.println("Implemention2 method1");}
    public void method2(){System.out.println("Implemention2 method2");}
}
class Implemention1Factoy implements Servicefactories{
    public  Service getservice(){
        return new Implemention1();
    }
}
class Implemention2Factoy implements Servicefactories{
    public  Service getservice(){
        return new Implemention2();
    }
}
public class Factories {
    public static void servicecomsumer(Servicefactories f){
        Service s=f.getservice();
        s.method1();
        s.method2();
    }
    public static void main(String[] args){
        servicecomsumer(new Implemention1Factoy());
        servicecomsumer(new Implemention2Factoy());
    }
}

 run:
Implemention1 method1
Implemention1 method2
Implemention2 method1
Implemention2 method2
BUILD SUCCESSFUL (total time: 0 seconds)

2.Games.java

interface Game{
    boolean move();
}
interface GameFactor{
    Game getgame();
}
class Checkers implements Game{
    private int moves=0;
    private static final int Moves=3;
    public boolean move(){
        System.out.println("Checkers move "+moves);
        return ++moves!=Moves;
    }
}
class CheckersFactory implements GameFactor{
    public Game getgame(){return new Checkers();}
}
class Chess implements Game{
    private int moves=0;
    private static final int Moves=4;
    public boolean move(){
        System.out.println("Chess move "+moves);
        return ++moves!=Moves;
    }
}
class ChessFactory implements GameFactor{
    public Game getgame(){return new Chess();}
}
public class Games {
    public static void playgame(GameFactor f){
        Game s=f.getgame();
        while(s.move());
    }
    public static void main(String[] args){
        playgame(new ChessFactory());
        playgame(new CheckersFactory());
    }
}

 run:
Chess move 0
Chess move 1
Chess move 2
Chess move 3
Checkers move 0
Checkers move 1
Checkers move 2
BUILD SUCCESSFUL (total time: 0 seconds)

3. Nestinginterfaces.java

class A{
    interface B{void f();}
    public class Bimp implements B{
        public void f(){System.out.println("A public class Bimp f()");}
    }
    private class Bimp2 implements B{
        public void f(){System.out.println("A private class Bimp2 f()");}
    }
    interface C{void f();}
    class Cimp implements C{
        public void f(){System.out.println("A class Cimp f()");}
    }
    private class Cimp2 implements C{
        public void f(){System.out.println("A private class Cimp2 f()");}
    }
    private interface D{void f();}
    private class Dimp implements D{
        public void f(){System.out.println("A private class Dimp f()");}
    }
    public class Dimp2 implements D{
        public void f(){System.out.println("A public class Dimp2 f()");}
    }
    public D getD(){return new Dimp2();}
    private D dref;
    public void receiveD(D d){
        dref=d;
        dref.f();
    }
}
interface E{
    interface G{void f();}
    public interface H{void f();}
    void g();
}
public class Nestinginterfaces {
    public class Bimp implements A.B{
        @Override
        public void f(){}
    }
    public class Cimp implements A.C{
        @Override
        public void f(){}
    }
    class Eimp implements E{
        @Override
        public void g() {  }   
    }
    class EGimp implements E.G{
        public void f() {}
    }
    public static void main(String[] args){
        A a=new A();
        A a2=new A();
        a2.receiveD(a.getD());
    }
}

 run:
A public class Dimp2 f()
BUILD SUCCESSFUL (total time: 0 seconds)

五、持有对象

1.AsListInference.java

import java.util.*;
class Snow{public void f(){System.out.print("Snow");}}
class Powder extends Snow{public void f(){System.out.print("Powder  ");}}
class Crusty extends Snow{public void f(){System.out.print("Crusty  ");}}
class Slush extends Snow{public void f(){System.out.print("Slush  ");}}
class Light extends Snow{public void f(){System.out.print("Light  ");}}
class Heavy extends Snow{public void f(){System.out.print("Heavy  ");}}
public class AsListInference {
    public static void main(String[] args){
        List<Snow> s1=Arrays.asList(new Crusty(),new Slush(),new Powder());
        System.out.print("s1: ");//s1
        for(Snow s:s1)s.f();
        System.out.println();
//        s1.add(new Light());
//        System.out.print("s1.add: ");//s1
//        for(Snow s:s1)s.f();
//        System.out.println();
        List<Snow> s2=new ArrayList<Snow>();
        Collections.addAll(s2, new Light(),new Heavy());
        System.out.print("s2.addAll: ");//s2
        for(Snow s:s2)s.f();
        System.out.println();
//        List<Snow> s3=new ArrayList<Snow>(s1);  
//        Snow[] sa=new Snow[s2.size()];
//        Collections.addAll(s3, s2.toArray(sa));
//        List<Snow> s4=Arrays.<Snow>asList(new Crusty(),new Slush(),new Powder());
//        
//        for(Snow s:s2)System.out.print(s+"   ");
//        System.out.println();
//        for(Snow s:s3)System.out.print(s+"   ");
//        System.out.println();
//        for(Snow s:s4)System.out.print(s+"   ");
//        System.out.println();
    }
}

 run:
s1: Crusty  Slush  Powder  
s2.addAll: Light  Heavy  
BUILD SUCCESSFUL (total time: 0 seconds)

2.Print.java

import java.util.*;
public class Print {
    public static void main(String[] args){
        System.out.println(fill(new ArrayList<String>()));
        System.out.println(fill(new LinkedList<String>()));
        System.out.println(fill(new HashSet<String>()));
        System.out.println(fill(new TreeSet<String>()));
        System.out.println(fill(new LinkedHashSet<String>()));
        System.out.println(fill(new HashMap<Integer,String>()));
        System.out.println(fill(new TreeMap<Integer,String>()));
        System.out.println(fill(new LinkedHashMap<Integer,String>()));
    }
    static Collection fill(Collection<String> cs){
        cs.add("cat");
        cs.add("dog");
        cs.add("rat");
        cs.add("cat");
        return cs;
    }
    static Map fill(Map<Integer,String> map){
        map.put(1,"dog");
        map.put(4,"cat");
        map.put(3,"rat");
        map.put(3,"bird");
        return map;
    }
}

 run:
[cat, dog, rat, cat]
[cat, dog, rat, cat]
[rat, cat, dog]
[cat, dog, rat]
[cat, dog, rat]
{1=dog, 3=bird, 4=cat}
{1=dog, 3=bird, 4=cat}
{1=dog, 4=cat, 3=bird}
BUILD SUCCESSFUL (total time: 0 seconds)

3.PriorityQueueTest.java

import java.util.*;
public class PriorityQueueTest {
    public static void main(String[] args){
        PriorityQueue<Integer> q=new PriorityQueue<Integer>();
        Random r=new Random(47);
        for(int i=0;i<10;i++){
            q.offer(r.nextInt(i+10));
        }
        QueueTest.print(q);
        List<Integer> l=Arrays.asList(23,31,45,54,65,78,46,65);
        q=new PriorityQueue<Integer>(l);
        QueueTest.print(q);
        q=new PriorityQueue<Integer>(l.size(),Collections.reverseOrder());
        q.addAll(l);
        QueueTest.print(q);
        List<String> list=new ArrayList<String>();
        for(String s:"my name is huo yu ying".split(" ")){
            list.add(s);
        }
        PriorityQueue<String> q1=new PriorityQueue<String>(list);
        QueueTest.print(q1);
        PriorityQueue<String> q2=new PriorityQueue<String>(list.size(),Collections.reverseOrder());
        q2.addAll(list);
        QueueTest.print(q2);
        
        Set<Character> s=new HashSet<Character>();
        for(Character c:"Huoyuying is beautiful girl".toCharArray()){
            s.add(c);
        }
        PriorityQueue<Character> s1=new PriorityQueue<Character>(s);
        QueueTest.print(s1);
        PriorityQueue<Character> s2=new PriorityQueue<Character>(s.size(),Collections.reverseOrder());
        s2.addAll(s);
        QueueTest.print(s2);
    }
}

 run:
0  1  1  1  1  1  3  5  8  14  
23  31  45  46  54  65  65  78  
78  65  65  54  46  45  31  23  
huo  is  my  name  ying  yu  
yu  ying  name  my  is  huo  
   H  a  b  e  f  g  i  l  n  o  r  s  t  u  y  
y  u  t  s  r  o  n  l  i  g  f  e  b  a  H     
BUILD SUCCESSFUL (total time: 0 seconds)

4.QueueTest.java

import java.util.*;
public class QueueTest {
    public static void main(String[] args){
        Queue<Integer> queue=new LinkedList<Integer>();
        Random r=new Random(47);
        for(int i=0;i<10;i++){
            queue.offer(r.nextInt(i+10));
        }
        print(queue);
        Queue<Character> queue1=new LinkedList<Character>();
        for(Character c:"Huoyuying".toCharArray()){
            queue1.offer(c);
        }
        print(queue1);
    }
    public static void print(Queue q){
        while(q.peek()!=null){
            System.out.print(q.remove()+"  ");
        }
        System.out.println();
    }
}

run:
8  1  1  1  5  14  3  1  0  1  
H  u  o  y  u  y  i  n  g  
BUILD SUCCESSFUL (total time: 0 seconds)

5.SimpleCollection.java

import java.util.*;
public class SimpleColletion {
    public static void main(String[] args){
        System.out.println("========add single==========");
        Collection<Integer> c=new ArrayList<Integer>();
        for(int i=0;i<10;i++)
        c.add(i);
        for(Integer i:c)
            System.out.print(i+" , ");
        System.out.println();
        System.out.println("========add groups==========");
        Collection<Integer> c1=new ArrayList<Integer>(Arrays.asList(1,2,3,4,5));
        Integer[] moreints={6,7,8,9,10};
        c1.addAll(Arrays.asList(moreints));
        Collections.addAll(c1, 11,12,13);
        for(Integer i:c1)System.out.print(i+" , ");
        System.out.println();
        List<Integer> list=Arrays.asList(1,2,3,4,5);
        list.set(1, 99);
        for(Integer i:list)System.out.print(i+" , ");
        System.out.println();
    }
}

run:
========add single==========
0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 
========add groups==========
1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 
1 , 99 , 3 , 4 , 5 , 
BUILD SUCCESSFUL (total time: 0 seconds)

 6.StackTest.java

import java.util.Stack;
public class StackTest {
    public static void main(String[] args){
        Stack<String> stack=new Stack<String>();
        for(String s:"my name is huoyuying".split(" "))
            stack.push(s);
        while(!stack.empty())
            System.out.print(stack.pop()+" ");
        System.out.println();
    }
}

run:
huoyuying is name my 
BUILD SUCCESSFUL (total time: 0 seconds)

六、迭代器

1.ForeachTest.java

import java.util.*;
public class ForeachTest {
    public static void main(String[] args){
        Collection<String> cs=new LinkedList<String>();
        Collections.addAll(cs, "my name is huoyuying".split(" "));
        for(String s:cs)
            System.out.print("'"+s+"'  " );
        System.out.println();
    }
}

run:
'my'  'name'  'is'  'huoyuying'  
BUILD SUCCESSFUL (total time: 0 seconds)

2. List1.java

import java.util.*;
class Snow{}
class Powder extends Snow{}
class Crusty extends Snow{}
class Slush extends Snow{}
class Light extends Snow{}
class Heavy extends Snow{}
public class List1 {
    public static void main(String[] args){
        List<Snow> s1=Arrays.asList(new Powder(),new Crusty(),new Slush());
        Iterator<Snow> it=s1.iterator();
        System.out.println("Method 1：");
        while(it.hasNext()){
            Snow s=it.next();
            System.out.print(s+"  ");
        }
        System.out.println();
        System.out.println("Method 2：");
        for(Snow ss:s1) 
            System.out.print(ss+"  ");
        System.out.println();
    }
}

run:
Method 1：
Powder@15db9742  Crusty@6d06d69c  Slush@7852e922  
Method 2：
Powder@15db9742  Crusty@6d06d69c  Slush@7852e922  
BUILD SUCCESSFUL (total time: 0 seconds)

七、异常处理

例子：Exceptions.java

class SimpleException extends Exception{}
public class Exceptions {
    public void f()throws SimpleException{
        System.out.println("Throw SimpleException from f()");
        throw new SimpleException();
    }
    public static void main(String[] args){
        Exceptions ted=new Exceptions();
        try{
            ted.f();
        }catch(SimpleException e){
            System.out.println("catch SimpleException from f()");
        }
    }
}

run:
Throw SimpleException from f()
catch SimpleException from f()
BUILD SUCCESSFUL (total time: 0 seconds)

八、String

1.SimpleFormat.java

public class SimpleFormat {
    public static void main(String[] args){
        int x=6;
        double y=5.434553;
        System.out.println("Row 1:[ "+x+" "+y+"]");
        System.out.format("Row 1:[ %d %f]
", x,y);
        System.out.printf("Row 1:[ %d %f]
", x,y);
    }
}

run:
Row 1:[ 6 5.434553]
Row 1:[ 6 5.434553]
Row 1:[ 6 5.434553]
BUILD SUCCESSFUL (total time: 0 seconds)

2.Turtle.java

import java.io.*;
import java.util.*;
public class Turtle {
    private String name;
    private Formatter f;
    public Turtle(String name,Formatter f){
        this.name=name;
        this.f=f;
    }
    public void move(int x,int y){
        f.format("%s the turtle is at (%d,%d)
",name,x,y);
    }
    public static void main(String[] args){
        PrintStream out=System.out;
        Turtle Sam=new Turtle("Sam",new Formatter(out));
        Turtle Holly=new Turtle("Holly",new Formatter(out));
        Sam.move(3, 5);
        Holly.move(4, 5);     
    }
}

run:
Sam the turtle is at (3,5)
Holly the turtle is at (4,5)
BUILD SUCCESSFUL (total time: 0 seconds)

3.UsingStringBuilder.java

import java.util.*;
public class UsingStringBuilder {
    public static Random r=new Random(47);
    public String toString(){
        StringBuilder result=new StringBuilder("[");
        for(int i=0;i<25;i++){
            result.append(r.nextInt(100));
            result.append(",");
        }
        result.delete(result.length()-1, result.length());
        result.append("]");
        return result.toString();
    }
    public static void main(String[] args){
        UsingStringBuilder u=new UsingStringBuilder();
        System.out.println(u);
    }
}

run:
[58,55,93,61,61,29,68,0,22,7,88,28,51,89,9,78,98,61,20,58,16,40,11,22,4]
BUILD SUCCESSFUL (total time: 0 seconds)

九、动态代理

1.Demo.java

interface A{
    public void method1();
    public void method2(String s);
}
class RealObject implements A{
    public void method1() {
        System.out.println("RealObject.method1()");
    }
    public void method2(String s) {
        System.out.println("RealObject.method2(): "+s);
    }
}
class SimpleProxy implements A{
    private A a;
    public SimpleProxy(A a){this.a=a;}
    public void method1() {
        System.out.println("SimpleProxy.method1()");
        a.method1();
    }
    public void method2(String s) {
        System.out.println("SimpleProxy.method2()");
        a.method2(s);
    }
}
public class Demo {
    public static void Show(A a){
        a.method1();
        a.method2("hello");
    }
    public static void main(String[] args){
        Show(new RealObject());
        System.out.println("=======================");
        Show(new SimpleProxy(new RealObject()));
    }
}

run:
RealObject.method1()
RealObject.method2(): hello
=======================
SimpleProxy.method1()
RealObject.method1()
SimpleProxy.method2()
RealObject.method2(): hello
BUILD SUCCESSFUL (total time: 0 seconds)

2.SimpleDynamicProxy.java

import java.lang.reflect.*;
public class SimpleDynamicProxy implements InvocationHandler {
    private Object proxied;
    public SimpleDynamicProxy(Object proxied){this.proxied=proxied;}
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("===proxy:"+proxy.getClass()+" method: "+method+" args: "+args);
        if(args!=null)
            for(Object arg:args)System.out.println(" "+arg);
        return method.invoke(proxied, args);
    }
    public static void main(String[] args){     
    }
}

run:
BUILD SUCCESSFUL (total time: 0 seconds)

十、

（未完待续，感谢支持♥♥♥）