Java面向对象深度

局部内部类

package ch6;

/**
 * Created by Jiqing on 2016/11/21.
 */
public class LocalInnerClass { // 局部内部类
    public static void main(String[] args) {
        // 定义局部内部类
        class InnerBase {
            int a;
        }

        // 定义局部内部类的子类
        class InnerSub extends InnerBase
        {
            int b;
        }

        // 创建局部内部类对象
        InnerSub is = new InnerSub();
        is.a = 5;
        is.b = 10;
        System.out.println("InnerSub对象的a和b实例变量是：" + is.a + "," + is.b);
    }
}

强制回收

package ch6;

/**
 * Created by Jiqing on 2016/11/21.
 */
public class Gc {
    public static void main(String[] args) {
        for(int i = 0; i<4;i++) {
            new Gc();
            // System.gc(); // 强制回收内存
            Runtime.getRuntime().gc();
        }
    }

    public void finalize() {
        System.out.println("正在回收内存");
    }
}

抽象类与抽象函数

package ch6.Shape;

/**
 * Created by Jiqing on 2016/11/21.
 */
public abstract class Shape {
    private String color;
    public abstract double calPerimeter();
    public abstract String getType();
    public Shape() {}
    public Shape(String color) {
        System.out.println("执行Shape构造器...");
        this.color = color;
    }
}

package ch6.Shape;

/**
 * Created by Jiqing on 2016/11/21.
 */
public class Triangle extends Shape {
    private double a;
    private double b;
    private double c;
    public Triangle(String color,double a,double b,double c){
        super(color);
        this.setSides(a,b,c);
    }

    public void setSides(double a,double b,double c){
        if (a >= b + c || b >= a + c|| c >= a + b) {
           System.out.println("三角形两边之和大于第三边...");
           return;
        }
        this.a = a;
        this.b = b;
        this.c = c;
    }

    public double calPerimeter() {
        return a + b + c;
    }

    public String getType() {
        return "三角形";
    }

    public static void main(String[] args) {
        Shape t = new Triangle("黑色",3,4,5);
        System.out.println(t.calPerimeter());
        System.out.println(t.getType());
    }
}

枚举类

package ch6.Enum;

/**
 * Created by Jiqing on 2016/11/21.
 */
public enum SeasonEnum { // 枚举类
    SPRING,SUMMER,FALL,WINTER;
}

package ch6.Enum;

/**
 * Created by Jiqing on 2016/11/21.
 */
public class Enum {
    public void judge(SeasonEnum s) {
        switch (s) {
            case SPRING:
                System.out.println("春暖花开,正好踏青");
                break;
            case SUMMER:
                System.out.println("夏日炎炎，适合游泳");
                break;
            case FALL:
                System.out.println("秋高气爽，进补及时");
                break;
            case WINTER:
                System.out.println("冬天寒冷，被窝赏雪");
        }
    }

    public static void main(String[] args) {
        for (SeasonEnum s : SeasonEnum.values()) {
            System.out.println(s);
        }
        new Enum().judge(SeasonEnum.FALL);
    }
}

package ch6.Enum;

/**
 * Created by Jiqing on 2016/11/21.
 */
public enum Operation { // 编译程序会生产5个class文件
    PLUS{ // 匿名内部子类
        public double eval(double x,double y) {
            return x + y;
        }
    },
    MINUS {
        public double eval(double x,double y) {
            return x - y;
        }
    },
    TIMES {
        public double eval(double x,double y) {
            return  x * y;
        }
    },
    DIVIDE {
        public double eval(double x,double y) {
            return x/y;
        }
    };
    public abstract double eval(double x,double y);

    public static void main(String[] args) {
        System.out.println(Operation.DIVIDE.eval(1.2,2.3));
    }
}