《 Java 核心技术》学习笔记

一）Java白皮书

二）基本程序设计结构

移步：https://www.jianshu.com/p/43f45dd0b22f

三）对象与类

例1 CalendarTest.java

import java.time.*;

public class CalendarTest
{
    public static void main(String[] args)
    {
        LocalDate date = LocalDate.now();//date = 2020-06-17
        int month = date.getMonthValue();//month = 6
        int today = date.getDayOfMonth();//today = 17
        System.out.println();
        System.out.println(date);
        
        date = date.minusDays(today-1);//date = date-16 = 2020-06-01
        System.out.println("Mon Tue Wen Thu Fri Sat Sun");
        while(date.getMonthValue() == month)
        {
            System.out.printf("%3d",date.getDayOfMonth());
            if(date.getDayOfMonth() == today)
                System.out.print("*");
            else
                System.out.print(" ");
            date = date.plusDays(1);//date = date+1
            int value = date.getDayOfWeek().getValue();//1 = Monday,...7 = Sunday
            if(value == 1) System.out.println();
        }
        System.out.println();
    }
}

例2 EmployeeTest.java

import java.time.*;

public class EmployeeTest{
    public static void main(String[]args){
        Employee[] staff=new Employee[3];
        staff[0]=new Employee("Lihua",75000,1989,5,2);
        staff[1]=new Employee("Wanggang",65000,1999,6,2);
        staff[2]=new Employee("Libai",105000,1979,7,29);
        for(Employee e:staff){
            e.raiseSalary(5);
        }
        for(Employee e:staff){
            System.out.println("name:"+e.getName());
            System.out.println("salary:"+e.getSalary());
            System.out.println("hireday:"+e.getHireday()+"\n");
        }
    }
}
class Employee{
    private String name;
    private float salary;
    private LocalDate hireday;
    public Employee(String n,float s,int year,int month,int day){
        name=n;
        salary=s;
        hireday=LocalDate.of(year,month,day);
    }
    public String getName(){
        return name;
    }
    public float getSalary(){
        return salary;
    }
    public LocalDate getHireday(){
        return hireday;
    }
    public void raiseSalary(double x){
        salary*=(1+x/100);
    }
}

例3 StaticTest.java

public class StaticTest{
    public static void main(String[]args){
        Employee[] staff=new Employee[3];
        staff[0]=new Employee("Lihua",75000);
        staff[1]=new Employee("Wanggang",65000);
        staff[2]=new Employee("Libai",105000);
        for(Employee e:staff){
            e.setId();
            System.out.println("name:"+e.getName());
            System.out.println("salary:"+e.getSalary());
            System.out.println("id:"+e.getId());
            System.out.println("next id:"+e.getnextId()+"\n");
        }
    }
}
class Employee{
    //静态域nextId
    static private int nextId=1;
    private String name;
    private double salary;
    private int id;
    public Employee(String n,double s){
        name=n;
        salary=s;
    }
    public String getName(){
        return name;
    }
    public double getSalary(){
        return salary;
    }
    public int getId(){
        return id;
    }
    //静态方法
    public static int getnextId(){
        return nextId;
    }
    public void setId(){
        id=nextId;
        nextId++;
    }
    //静态的main方法
    public static void main(String[]args){
        Employee e=new Employee("Xiaoming",50000);
        System.out.println("name:"+e.getName());
        System.out.println("salary:"+e.getSalary());
    }
}
// 因为有中文注释，编译命令：>> javac -encoding UTF-8 StaticTest.java

例3 ParamTest.java

public class ParamTest{
    public static void main(String[]args){
        //test1,fail
        double percent=10;
        System.out.println("before percent:"+percent);
        tripleValue(percent);
        System.out.println("after percent:"+percent+"\n");
        //test2,success
        Employee e=new Employee("Lihua",50000);
        System.out.println("before salary:"+e.getSalary());
        tripleSalary(e);
        System.out.println("after salary:"+e.getSalary()+"\n");
        //test3,fail
        Employee a=new Employee("A",50000);
        Employee b=new Employee("B",50000);
        System.out.println("before a:"+a.getName()+"   b:"+b.getName());
        swap(a,b);
        System.out.println("after a:"+a.getName()+"   b:"+b.getName()+"\n");
    }
    public static void tripleValue(double percent){
        percent*=3;
        System.out.println("End percent:"+percent);
    }
    public static void tripleSalary(Employee x){
        x.raiseSalary(200);
        System.out.println("End salary:"+x.getSalary());
    }
    public static void swap(Employee a,Employee b){
        Employee temp=a;
        a=b;
        b=temp;
        System.out.println("End a:"+a.getName()+"   b:"+b.getName());
    }
}
class Employee{
    private String name;
    private float salary;
    
    public Employee(String n,float s){
        name=n;
        salary=s;
    }
    public String getName(){
        return name;
    }
    public float getSalary(){
        return salary;
    }
    public void raiseSalary(double x){
        salary*=(1+x/100);
    }
}

例4 ConstructorTest.java

import java.util.*;

public class ConstructorTest{
    public static void main(String[]args){
        Employee[] staff=new Employee[3];
        staff[0]=new Employee("Harry",40000);
        staff[1]=new Employee(60000);
        staff[2]=new Employee();
        for(Employee e:staff){
            System.out.println("name:"+e.getName());
            System.out.println("salary:"+e.getSalary());
            System.out.println("id:"+e.getId()+"\n");
        }
    }
}
class Employee{
    private static int nextId;
    private int id;
    private String name="";
    private double salary;
    //静态初始化块
    static {
        Random generator=new Random();
        nextId=generator.nextInt(10000);//nextId:0~9999
    }
    {
        id=nextId;
        nextId++;
    }
    //对象初始化块
    public Employee(String n,double s){
        name=n;
        salary=s;
    }
    //用this调用另一个构造器
    public Employee(double s){
        this("Employee #"+nextId,s);
    }
    //无参数构造器
    public Employee()
    {  } 
    public String getName(){
        return name;
    }
    public double getSalary(){
        return salary;
    }
    public int getId(){
        return id;
    }
}

例5 PackageTest.java

import com.du1in9.Employee;
import static java.lang.System.*;

public class PackageTest{
    public static void main(String[]args){
        Employee e=new Employee("Lihua",50000,1949,10,1);
        e.raiseSalary(5);
        out.println("name:"+e.getName());
        out.println("salary:"+e.getSalary());
        out.println("hireday:"+e.getHireday()+"\n");
    }
}

com/du1in9/Employee.java

package com.du1in9;
import java.time.*;

public class Employee{
    private String name;
    private double salary;
    private LocalDate hireday;
    
    public Employee(String n,double s,int year,int month,int day){
        name=n;
        salary=s;
        hireday=LocalDate.of(year,month,day);
    }
    public String getName(){
        return name;
    }
    public double getSalary(){
        return salary;
    }
    public LocalDate getHireday(){
        return hireday;
    }
    public void raiseSalary(double x){
        salary*=(1+x/100);
    }
}

四）继承

例1 inheritance/ManagerTest.java

package inheritance;


public class ManagerTest
{
   public static void main(String[] args)
   {
      Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
      boss.setBonus(5000);

      Employee[] staff = new Employee[3];
      staff[0] = boss;
      staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
      staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15);

      for (Employee e : staff)
         System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());
   }
}

inheritance/Employee.java

package inheritance;

import java.time.*;


public class Employee
{
   private String name;
   private double salary;
   private LocalDate hireDay;

   public Employee(String name, double salary, int year, int month, int day)
   {
      this.name = name;
      this.salary = salary;
      hireDay = LocalDate.of(year, month, day);
   }
   public String getName()
   {
      return name;
   }
   public double getSalary()
   {
      return salary;
   }
   public LocalDate getHireDay()
   {
      return hireDay;
   }
   public void raiseSalary(double byPercent)
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }
}

inheritance/Manager.java

package inheritance;


public class Manager extends Employee
{
   private double bonus;
   
   public Manager(String name, double salary, int year, int month, int day)
   {
      super(name, salary, year, month, day);
      bonus = 0;
   }
   public double getSalary()
   {
      double baseSalary = super.getSalary();
      return baseSalary + bonus;
   }
   public void setBonus(double b)
   {
      bonus = b;
   }
}

例2 类，超类，子类 ABC/Employee.java

package ABC;
import java.time.*;

abstract class Person{
   public abstract String getDescription();
   private String name;

   public Person(String n){
      this.name = n;
   }
   public String getName(){
      return name;
   }
}

class Student extends Person{
   private String major;
   public Student(String n, String m){
      super(n);
      this.major = m;
   }
   public String getDescription(){
      return "a student majoring in " + major;
   }
}

public class Employee extends Person{
   private double salary;
   private LocalDate hireDay;

   public Employee(String n, double s, int y, int m, int d){
      super(n);
      this.salary = s;
      hireDay = LocalDate.of(y, m, d);
   }
   public double getSalary(){
      return salary;
   }
   public LocalDate getHireDay(){
      return hireDay;
   }
   public String getDescription(){
      return String.format("an employee with a salary of $%.2f", salary);
   }
   public void raiseSalary(double p){
      double raise = salary * p/100;
      salary += raise;
   }
}

class PersonTest{
   public static void main(String[] args){
      Person[] people = new Person[2];
      people[0] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
      people[1] = new Student("Maria Morris", "computer science");
      
      for (Person p : people){
         System.out.println(p.getName() + ", " + p.getDescription());
      }
   }
}

例3 equals/Employee.java

import java.time.*;
import java.util.Objects;

public class Employee{
   private String name;
   private double salary;
   private LocalDate hireDay;
   public Employee(String n, double s, int y, int m, int d){
      this.name = n;
      this.salary = s;
      hireDay = LocalDate.of(y, m, d);
   }
   public String getName(){
      return name;
   }
   public double getSalary(){
      return salary;
   }
   public LocalDate getHireDay(){
      return hireDay;
   }
   public void raiseSalary(double p){
      double raise = salary * p/100;
      salary += raise;
   }
   public boolean equals(Object o){
      if (o == this) return true;
      if (o == null) return false;
      if (getClass() != o.getClass()) return false;
      Employee other = (Employee) o;
      return Objects.equals(name, other.name) && salary == other.salary && Objects.equals(hireDay, other.hireDay);
   }
   public int hashCode(){
      return Objects.hash(name, salary, hireDay); 
   }
   public String toString(){
      return getClass().getName() + "[ name = " + name + ", salary = " + salary + ", hireDay = " + hireDay + " ]";
   }
   public static void main(String[] args){
      Employee A1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
      Employee A2 = A1;
      Employee A3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
      Employee bob = new Employee("Bob Brandson", 50000, 1989, 10, 1);

      System.out.println("A1 == A2: " + (A1 == A2));
      System.out.println("A1 == A3: " + (A1 == A3));
      System.out.println("A1.equals(A3): " + A1.equals(A3));
      System.out.println("A1.equals(bob): " + A1.equals(bob));
      System.out.println("bob.toString(): " + bob);

      Manager carl = new Manager("Carl Cracker", 80000, 1987, 12, 15);
      Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
      boss.setBonus(5000);
      
      System.out.println("boss.toString(): " + boss);
      System.out.println("carl.equals(boss): " + carl.equals(boss));
      System.out.println("A1.hashCode(): " + A1.hashCode());
      System.out.println("A3.hashCode(): " + A3.hashCode());
      System.out.println("bob.hashCode(): " + bob.hashCode());
      System.out.println("carl.hashCode(): " + carl.hashCode());
   }
}

class Manager extends Employee{
   private double bonus;
   public Manager(String n, double s, int y, int m, int d){
      super(n, s, y, m, d);
      bonus = 0;
   }
   public double getSalary(){
      double baseSalary = super.getSalary();
      return baseSalary + bonus;
   }
   public void setBonus(double b){
      this.bonus = b;
   }
   public boolean equals(Object o){
      if (!super.equals(o)) return false;
      Manager other = (Manager) o;
      return bonus == other.bonus;
   }
   public int hashCode(){
      return super.hashCode() + 17 * new Double(bonus).hashCode();
   }
   public String toString(){
      return super.toString() + "[ bonus = " + bonus + " ]";
   }
}

例4 arrayList/ArrayListTest.java

package arrayList;
import java.time.LocalDate;
import java.util.ArrayList;

class Employee{
   private String name;
   private double salary;
   private LocalDate hireDay;
   // 构造函数
   public Employee(String n, double s, int y, int m, int d){
      this.name = n;
      this.salary = s;
      hireDay = LocalDate.of(y, m, d);
   }
   // 得到名字
   public String getName(){
      return name;
   }
   // 发薪日期
   public double getSalary(){
      return salary;
   }
   // 雇用日期
   public LocalDate getHireDay(){
      return hireDay;
   }
   // 加薪日期
   public void raiseSalary(double p){
      double raise = salary * p/100;
      salary += raise;
   }
}

public class ArrayListTest{
   public static void main(String[] args){
      ArrayList<Employee> staff = new ArrayList<>();
      staff.add(new Employee("Carl Cracker", 75000, 1987, 12, 15));
      staff.add(new Employee("Harry Hacker", 50000, 1989, 10, 1));
      staff.add(new Employee("Tony Tester", 40000, 1990, 3, 15));
      // for each 循环
      for (Employee e : staff){
          e.raiseSalary(5);
      }
      for (Employee e : staff){
          System.out.println("name = " + e.getName() + ", salary = " + e.getSalary() + ", hireDay = " + e.getHireDay());
      }
   }
}

例5 enums/EnumTest.java

package enums;
import java.util.*;

public class EnumTest{  
   public static void main(String[] args){  
      Scanner in = new Scanner(System.in);
      System.out.print("Enter a size: (small, medium, large, extra_large) ");
      // 将输入字符串转换为大写
      String input = in.next().toUpperCase();
      Size s = Enum.valueOf(Size.class, input);
      // 输出尺寸
      System.out.println("size = " + s);
      // 输出尺寸缩写
      System.out.println("abbreviation = " + s.get());
      if (s == Size.extra_large){ System.out.println("Good job!"); }          
   }
}

enum Size{
   small("S"), medium("M"), large("L"), extra_large("XL");
   private Size(String a){ this.abbreviation = a; }
   public String get(){ return abbreviation; }
   // abbreviation：缩写
   private String abbreviation;
}

例6 reflection/ReflectionTest.java

package reflection;

import java.util.*;
import java.lang.reflect.*;

public class ReflectionTest{
   public static void main(String[] args){
      String name;
      if (args.length > 0) name = args[0];
      else{
         Scanner in = new Scanner(System.in);
         System.out.println("Enter class name (e.g. java.util.Date): ");
         name = in.next();
      }
      try{
         Class cl = Class.forName(name);
         Class supercl = cl.getSuperclass();
         String modifiers = Modifier.toString(cl.getModifiers());
         if (modifiers.length() > 0) System.out.print(modifiers + " ");
         System.out.print("class " + name);
         if (supercl != null && supercl != Object.class) System.out.print(" extends " + supercl.getName());

         System.out.print("\n{\n");
         printConstructors(cl);
         System.out.println();
         printMethods(cl);
         System.out.println();
         printFields(cl);
         System.out.println("}");
      }
      catch (ClassNotFoundException e){
         e.printStackTrace();
      }
      System.exit(0);
   }

   public static void printConstructors(Class cl){
      Constructor[] constructors = cl.getDeclaredConstructors();
      for (Constructor c : constructors){
         String name = c.getName();
         System.out.print("   ");
         String modifiers = Modifier.toString(c.getModifiers());
         if (modifiers.length() > 0) System.out.print(modifiers + " ");         
         System.out.print(name + "(");
         Class[] paramTypes = c.getParameterTypes();
         for (int j = 0; j < paramTypes.length; j++){
            if (j > 0) System.out.print(", ");
            System.out.print(paramTypes[j].getName());
         }
         System.out.println(");");
      }
   }

   public static void printMethods(Class cl){
      Method[] methods = cl.getDeclaredMethods();
      for (Method m : methods){
         Class retType = m.getReturnType();
         String name = m.getName();
         System.out.print("   ");
         String modifiers = Modifier.toString(m.getModifiers());
         if (modifiers.length() > 0) System.out.print(modifiers + " ");         
         System.out.print(retType.getName() + " " + name + "(");
         Class[] paramTypes = m.getParameterTypes();
         for (int j = 0; j < paramTypes.length; j++){
            if (j > 0) System.out.print(", ");
            System.out.print(paramTypes[j].getName());
         }
         System.out.println(");");
      }
   }

   public static void printFields(Class cl){
      Field[] fields = cl.getDeclaredFields();
      for (Field f : fields){
         Class type = f.getType();
         String name = f.getName();
         System.out.print("   ");
         String modifiers = Modifier.toString(f.getModifiers());
         if (modifiers.length() > 0) System.out.print(modifiers + " ");         
         System.out.println(type.getName() + " " + name + ";");
      }
   }
}

例7 ObjectAnalyzerTest.java

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;

class ObjectAnalyzer{
   private ArrayList<Object> x = new ArrayList<>();
   public String toString(Object o){
      if (o == null) return  "  null ";
      if (x.contains(o)) return  "  ... ";
      x.add(o);
      Class cl = o.getClass();
      if (cl == String.class) return (String) o;
      if (cl.isArray()){
         String r = cl.getComponentType() +  "  []{ ";
         for (int i = 0; i < Array.getLength(o); i++){
            if (i > 0) r +=  "  , ";
            Object y = Array.get(o, i);
            if (cl.getComponentType().isPrimitive()) r += y;
            else r += toString(y);
         }
         return r + "}";
      }
      String r = cl.getName();
      do{
         r += "[";
         Field[] fields = cl.getDeclaredFields();
         AccessibleObject.setAccessible(fields, true);
         for (Field f : fields){
            if (!Modifier.isStatic(f.getModifiers())){
               if (!r.endsWith("[")) r += ",";
               r += f.getName() + "=";
               try{
                  Class t = f.getType();
                  Object y = f.get(o);
                  if (t.isPrimitive()) r += y;
                  else r += toString(y);
               }
               catch (Exception e){
                  e.printStackTrace();
               }
            }
         }
         r += "]";
         cl = cl.getSuperclass();
      }
      while (cl != null);
      return r;
   }
}

public class ObjectAnalyzerTest{
   public static void main(String[] args){
      ArrayList<Integer> s = new ArrayList<>();
      for (int i = 1; i <= 5; i++)
         s.add(i * i);
      System.out.println(new ObjectAnalyzer().toString(s));
   }
}

例8 CopyOfTest.java

import java.lang.reflect.*;
import java.util.*;

public class CopyOfTest{
   public static void main(String[] args){
      int[] a = { 1, 2, 3 };
      a = (int[]) goodCopyOf(a, 10);
      System.out.println(Arrays.toString(a));

      String[] b = { "Tom", "Dick", "Harry" };
      b = (String[]) goodCopyOf(b, 10);
      System.out.println(Arrays.toString(b));

      System.out.println("The following call will generate an exception.");
      b = (String[]) badCopyOf(b, 10);
   }

   public static Object[] badCopyOf(Object[] a, int L){
      Object[] newArray = new Object[L];
      System.arraycopy(a, 0, newArray, 0, Math.min(a.length, L));
      return newArray;
   }
   public static Object goodCopyOf(Object a, int L){  
      Class cl = a.getClass();
      if (!cl.isArray()) return null;
      Class componentType = cl.getComponentType();
      int length = Array.getLength(a);
      Object newArray = Array.newInstance(componentType, L);
      System.arraycopy(a, 0, newArray, 0, Math.min(length, L));
      return newArray;
   }
}

例9 M.java

import java.lang.reflect.*;

public class M{
   public static void main(String[] args) throws Exception{
      Method square = M.class.getMethod("square", double.class);
      Method sqrt = Math.class.getMethod("sqrt", double.class);
      print(1, 10, 10, square);
      print(1, 10, 10, sqrt);
   }
   public static double square(double x){
      return x * x;
   }
   // f 是 Method 类对象
   public static void print(double A, double B, int n, Method f){
      System.out.println(f);
      double dx = (B - A) / (n - 1);
      for (double x = A; x <= B; x += dx){
         // try catch throw 异常机制
         try{
            // invoke 调用本类的静态方法
            double y = (Double) f.invoke(null, x);
            System.out.printf("%10.4f | %10.4f%n", x, y);
         }
         catch (Exception e){
            e.printStackTrace();
         }
      }
   }
}

五）接口，lambda 表达式，内部类

例1 EmployeeSortTest.java

import java.util.*;

class Employee implements Comparable<Employee>{
   private String name;
   private double salary;
   // 构造函数
   public Employee(String n, double s){
      this.name = n;
      this.salary = s;
   }
   public String getName(){
      return name;
   }
   public double getSalary(){
      return salary;
   }
   // 覆盖 Comparable 中的抽象方法 compareTo(Employee)
   public int compareTo(Employee o){
      return Double.compare(salary, o.salary);
   }
}
public class EmployeeSortTest{
   public static void main(String[] args){
      Employee[] e = new Employee[3];
      e[0] = new Employee("Harry Hacker", 35000);
      e[1] = new Employee("Carl Cracker", 75000);
      e[2] = new Employee("Tony Tester", 38000);
      // 工资排序
      Arrays.sort(e);
      for (Employee x : e)
         System.out.println("name = " + x.getName() + ", salary=" + x.getSalary());
   }
}

例2 TimerTest.java

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer; 

public class TimerTest{  
   public static void main(String[] args){  
      ActionListener l = new Time();
      // 第一个参数时间间隔，第二个参数监听器对象    
      Timer t = new Timer(10000, l);
      t.start();
      JOptionPane.showMessageDialog(null, "Quit program?");
      System.exit(0);
   }
}
class Time implements ActionListener{  
   public void actionPerformed(ActionEvent event){ 
      System.out.println("Time: " + new Date());
      Toolkit.getDefaultToolkit().beep();
   }
}

例3 CloneTest.java

import java.util.Date;
import java.util.GregorianCalendar;

class Employee implements Cloneable{
   private String name;
   private double salary;
   private Date hireDay;

   public Employee(String n, double s){
      this.name = n;
      this.salary = s;
      hireDay = new Date();
   }
   public Employee clone() throws CloneNotSupportedException{
      Employee c = (Employee) super.clone();
      c.hireDay = (Date) hireDay.clone();
      return c;
   }
   public void setHireDay(int y, int m, int d){
      Date x = new GregorianCalendar(y, m - 1, d).getTime();
      hireDay.setTime(x.getTime());
   }
   public void raiseSalary(double p){
      double raise = salary * p/100;
      salary += raise;
   }
   //////////////////////////
   public String toString(){
      return "Employee [ name = " + name + " , salary = " + salary + " , hireDay = " + hireDay + " ]";
   }
   //////////////////////////
}
public class CloneTest{
   public static void main(String[] args){
      try{
         Employee a = new Employee("John Q. Public", 50000);
         a.setHireDay(2000, 1, 1);
         Employee b = a.clone();
         b.raiseSalary(10);
         b.setHireDay(2002, 12, 31);
         System.out.println("a = " + a);
         System.out.println("b = " + b);
      }
      catch (CloneNotSupportedException e){
         e.printStackTrace();
      }
   }
}

例4 LambdaTest.java

import java.util.*;
import javax.swing.*;
import javax.swing.Timer;

public class LambdaTest{
   public static void main(String[] args){
      String[] p = new String[] { "Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune" };
      System.out.println(Arrays.toString(p));
      System.out.println("Sorted in order: ");
      Arrays.sort(p);
      System.out.println(Arrays.toString(p));
      System.out.println("Sorted by length: ");
      Arrays.sort(p, (first, second) -> first.length() - second.length());
      System.out.println(Arrays.toString(p));
      // 1000ms = 1s
      Timer t = new Timer(1000, event -> System.out.println("The time is: " + new Date()));
      t.start();   
      JOptionPane.showMessageDialog(null, "Quit program?");
      System.exit(0);         
   }
}

例5 InnerClassTest.java

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;

public class InnerClassTest{
   public static void main(String[] args){
      Talk c = new Talk(1000, true);
      c.start();
      JOptionPane.showMessageDialog(null, "Quit program ?");
      System.exit(0);
   }
}
class Talk{
   private int interval;
   private boolean beep;
   public Talk(int i, boolean b){
      this.interval = i;
      this.beep = b;
   }
   public void start(){
      ActionListener x = new Printer();
      Timer t = new Timer(interval, x);
      t.start();
   }
   public class Printer implements ActionListener{
      public void actionPerformed(ActionEvent event){
         System.out.println("Time: " + new Date());
         if (beep) Toolkit.getDefaultToolkit().beep();
      }
   }
}

例6 AnonymousInnerClassTest.java

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;

public class AnonymousInnerClassTest{
   public static void main(String[] args){
      Talk c = new Talk();
      c.start(1000, true);
      JOptionPane.showMessageDialog(null, "Quit program ?");
      System.exit(0);
   }
}
class Talk{
   public void start(int interval, boolean beep){
      ActionListener l = new ActionListener(){
            public void actionPerformed(ActionEvent event){
               System.out.println("Time: " + new Date());
               if (beep) Toolkit.getDefaultToolkit().beep();
            }
         };
      Timer t = new Timer(interval, l);
      t.start();
   }
}

例7 StaticInnerClassTest.java

public class StaticInnerClassTest{
   public static void main(String[] args){
      double[] d = new double[10];
      for (int i = 0; i < d.length; i++){
          d[i] = 100 * Math.random();
          System.out.println(d[i]);
      }
      Array.Pair p = Array.minmax(d);
      System.out.println("min = " + p.getA());
      System.out.println("max = " + p.getB());
   }
}
class Array{
   public static class Pair{
      private double A;
      private double B;
      public Pair(double a, double b){
         A = a; 
         B = b;
      }
      public double getA(){
         return A;
      }
      public double getB(){
         return B;
      }
   }
   public static Pair minmax(double[] V){
      double min = Double.POSITIVE_INFINITY;
      double max = Double.NEGATIVE_INFINITY;
      for (double v : V){
         if (min > v) min = v;
         if (max < v) max = v;
      }
      return new Pair(min, max);
   }
}

例8 ProxyTest.java

import java.lang.reflect.*;
import java.util.*;

public class ProxyTest{
   public static void main(String[] y){
      Object[] m = new Object[1000];
      for (int i = 0; i < m.length; i++){
         Integer x = i + 1;
         InvocationHandler h = new Trace(x);
         Object proxy = Proxy.newProxyInstance(null, new Class[] { Comparable.class } , h);
         m[i] = proxy;
      }
      Integer key = new Random().nextInt(m.length) + 1;
      int result = Arrays.binarySearch(m, key);
      if (result >= 0) System.out.println( m[result] );
   }
}
class Trace implements InvocationHandler{
   private Object target;
   public Trace(Object t){
      target = t;
   }
   public Object invoke(Object proxy, Method m, Object[] y) throws Throwable{
      System.out.print(target);
      System.out.print("." + m.getName() + "(");
      if (y != null){
         for (int i = 0; i < y.length; i++){
            System.out.print(y[i]);
            if (i < y.length - 1) System.out.print(", ");
         }
      }
      System.out.println(")");
      return m.invoke(target, y);
   }
}

《 Java 核心技术 》学习笔记

《 Java 核心技术》学习笔记