Java 内部类

Posted 2021-03-04 小海_macro

public class TestInnerClass {
    public static int field = 1;
    protected int field1 = 2;
    int field2 = 3;
    private int field3 = 4;

    //静态代码块
    /*static {
        System.out.println(field);
    }*/

    public TestInnerClass(){
        NorInner norInner = new NorInner();
        System.out.println(norInner.field1Inner);
        System.out.println(norInner.field2Inner);
        System.out.println(norInner.field3Inner);
        System.out.println(norInner.fieldInner);
        //System.out.println(fieldInner);
    }

    //普通内部类
    public class NorInner{
        public int fieldInner = 1;
        protected int field1Inner = 2;
        int field2Inner = 3;
        private int field3Inner = 4;
        int field = 3;

        public NorInner(){
            System.out.println("内部类field:"+field);
            System.out.println("外部类field:"+TestInnerClass.this.field);
            System.out.println(field1);
            System.out.println(field2);
            System.out.println(field3);
        }
    }

    private void print(){
        StaticInner staticInner = new StaticInner();
        System.out.println(staticInner.field1Inner);
    }

    //静态内部类
    static class StaticInner{
        public int fieldInner = 1;
        protected int field1Inner = 2;
        int field2Inner = 3;
        private int field3Inner = 4;
        static int i=0;

        public StaticInner(){
            System.out.println(field);
            System.out.println(i);
        }
    }

    //自定义接口
    interface OnclickListener{
        void onClick(Object object);
        static int i =1;
        final int NUMB = 124;
        int a = 0;

        void print();
        //void print();
        /*static final void print1(){
            System.out.println("hello");
        }*/
    }

    //匿名内部类
    private void clickInner(){
        OnclickListener oc = new OnclickListener() {
            @Override
            public void onClick(Object object) {
                System.out.println("对象"+object+"被点击");
            }
            public void print(){
                System.out.println("匿名内部类打印");
                System.out.println(i+NUMB+a);
            }
        };
        oc.onClick(new Object(){
            @Override
            public String toString() {
                return super.toString();
            }
        });
        oc.onClick(2);
        oc.print();
    }

    //局部内部类;一般采用匿名内部类
    public static void main(String[] args) {
        TestInnerClass tic = new TestInnerClass();
        System.out.println("普通内部类：");
        //TestInnerClass.NorInner norInner = new tic.NorInner();
        TestInnerClass.NorInner norInner = tic.new NorInner();

        System.out.println("匿名内部类：");

        tic.clickInner();
        System.out.println("静态内部类：");
        StaticInner staticInner1 = new StaticInner();
        System.out.println(field);

    }
}

//作用域问题

public class testInnerVariable {
    class NormalClass{
        //普通内部类不能有静态变量、方法
        int numb = 1;
        public void print(){
            System.out.println("普通内部类numb:"+numb);
        }
        //static void test(){}
    }
    static class StaticClass{
        static int numb = 2;
        public void print(){
            System.out.println("静态内部类numb:"+numb);
        }
        static void test(){
            System.out.println("hello");
        }
    }
    interface Anonymity{
        static int numb = 3;

        public static void print() {
            System.out.println("接口numb:"+numb);
        }
    }
    private void print(){
        Anonymity anonymity = new Anonymity() {
            @Override
            public String toString() {
                System.out.println("匿名内部类变量numb："+numb);
                return super.toString();
            }
        };
        anonymity.toString();
        Anonymity.print();
        //静态方法不支持对象访问
        //anonymity.print();

        //局部内部类
        class LocalClass{
            //不支持静态变量
            int numb = 1;
            public void print(){
                System.out.println("局部内部类numb"+numb);
            }
            //不支持静态方法
            /*public static void test(){
                System.out.println("hello");
            }*/
        }
        LocalClass localClass = new LocalClass();
        localClass.print();
    }

    /*public staic void test(){

    }*/
    public static void main(String[] args) {

    }

}

??接口的静态方法不支持对象访问

跟虚拟机有关：填坑！！高级应用

典型内存泄漏案例

public class MemoryLeakTest {

    //抽象类，模拟组件类
    static abstract class Component{
        final void onCreat(){
            creat();
        }
        final void onDestroy(){
            destroy();
        }

        abstract void creat();
        abstract void destroy();
    }

    //具体实现子类————组件
    static class MyComponet extends Component{
        Mywindow mywindow;
        static OnclickListener onclickListener;

        @Override
        void creat() {
            onclickListener = new OnclickListener() {
                @Override
                public void onClick(Object object) {
                    System.out.println("组件： "+object+"被点击！");
                }
            };
            mywindow = new Mywindow();
            mywindow.setOnclickListener(onclickListener);
        }

        @Override
        void destroy() {
            //this.mywindow.getOnclickListener();
            mywindow.removeClickListener();
        }
    }

    //可视化控件
    static class Mywindow{
        OnclickListener onclickListener;

        public OnclickListener getOnclickListener(){
            return onclickListener;
        }
        public void setOnclickListener(OnclickListener onclickListener){
            this.onclickListener = onclickListener;
        }
        public void removeClickListener(){
            this.onclickListener = null;
        }
    }


    //监听器接口
    interface OnclickListener{
        void onClick(Object object);
    }

    public static void main(String[] args) {
        MyComponet myComponet = new MyComponet();
        myComponet.creat();
        myComponet.destroy();
        System.gc();
        System.out.println("");


    }
}