json deepCopy

// 比 JSON.parse(JSON.stringify(data)) 還略慢

module.exports = deepCopy;

let jobList = [];

// for test
// 與 JSON.stringify() 對比速度用
function deepCopy(value) {
    // debugger;

    let dataSet = new DataSet(value);
    jobList.push(dataSet);

    let index = 0;

    while ((dataSet = jobList[index++]) != null) {
        // debugger;

        let _value = dataSet.originalValue;

        if (Array.isArray(_value)) {
            for (let i = 0; i < _value.length; i++) {
                let v = _value[i];
                let ds = new DataSet(v, dataSet, i);
                jobList.push(ds);
            }

        } else if (typeof (_value) == "object") {
            for (let k in _value) {
                let v = _value[k];
                let ds = new DataSet(v, dataSet, k);
                jobList.push(ds);
            }
        } else {
            continue;
        }
    }
    //-----------------------
    let res;
    let d;

    while ((d = jobList.pop()) != null) {
        res = d;
        d.solve();
    }

    return res.value;
}
//======================================

function DataSet(v, p, k) {

    this.parent; // DataSet
    this.parentKey;
    this.value;
    this.originalValue;

    this.__construct(v, p, k);
}

(function () {
    this.__construct = function (v, p, k) {

        this.originalValue = v;

        if (p) {
            this.parent = p;
            this.parentKey = k;
        }

        this._makeValue();
    };
    //--------------------------------------
    this._makeValue = function () {
        if (Array.isArray(this.originalValue)) {
            this.value = [];
        } else if (typeof (this.originalValue) == "object") {
            this.value = {};
        } else {
            this.value = this.originalValue;
        }
    };
    //--------------------------------------
    this.solve = function () {

        if (this.parent == null) {
            return;
        }

        let data = this.parent.value;
        data[this.parentKey] = this.value;

        this._destory();
    };
    //--------------------------------------
    this._destory = function () {
        this.parent = undefined;
        this.parentKey = undefined;
        this.value = undefined;
        this.originalValue = undefined;
    };
}).call(DataSet.prototype);

worker 與 java 執行續的不同

worker 父執行緒與子執行緒並不會交叉執行


let child = new Worker("./child_1.js");
        let it;

        child.onmessage = function(e) {

            let data = e.data;
            console.log(`child ${data.index}`);

            // 確保 parent loop 與 child 幾乎同時執行
            it.next();
        };

        function* parentLoop(){

            for (var i = 0; i < 100; i++) {
                console.log(`parent ${i}`);
            }

            console.dir("parent finish");
        }

        function click() {
            it = parentLoop();
            child.postMessage({});
        }
-----------------------------------------------------------------
onmessage = function(oEvent) {

    for (var i = 0; i < 100; i++) {
        postMessage({index:i});
    }

};

javascript ES6

http://es6.ruanyifeng.com/#docs/proxy

front-end framwork

https://www.zcfy.cc/article/writing-a-javascript-framework-data-binding-with-es6-proxies-risingstack-1655.html

https://nx-framework.com/docs/basics/summary

https://github.com/nx-js/observer-util

java 從網址取得 json data 並解析

package test_4;

import org.json.*;
import java.net.*;
import java.io.*;
import static java.lang.System.out;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author xman
 */
public class T_1 {

    public static String getURLContent(String urlPath) throws MalformedURLException, IOException {
        String content = "";
        HttpURLConnection connection = null;
        BufferedReader in;

        URL url = null;

        url = new URL(urlPath);

        URLConnection urlConnection = url.openConnection();

        if (urlConnection instanceof HttpURLConnection) {
            connection = (HttpURLConnection) urlConnection;
        } else {
            System.out.println("请输入 URL 地址");
            return content;
        }
        in = new BufferedReader(
                new InputStreamReader(connection.getInputStream()));

        String current;
        while ((current = in.readLine()) != null) {
            content += current;
        }

        return content;
    }

    public static void main(String[] args) throws Exception {
        String htmlContent = getURLContent("http://localhost:8081/test_1/JSON/t_1.php");

        // out.println(htmlContent);
        JSONObject j;

        j = new JSONObject(htmlContent);

        Iterator<String> it = j.keys();;

        while (it.hasNext()) {
            String key = it.next();

            Object o_1 = j.get(key);
            out.printf("(%s)=>(%s)\n", key, o_1.toString());
        }
    }
}

java 閉包 範例

package test_4;

import static java.lang.System.out;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author xman
 */
public class T_2 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        int a = 5;

        T2_Closure t = (new T2_Closure<Object, Void>() {
            @Override
            public Void callback(Object in) {

                // 引用 a
                out.printf("callback(%s)\n", a);
                return null;
            }
        });

        t.callback(null);
        //------------------------------------

        T2_Query q = new T2_Query();

        q.query(new T2_Closure<T2_Query, Void>() {
            @Override
            public Void callback(T2_Query in) {

                String res = in.name + " : " + a;
                out.println(res);
                return null;
            }
        });
    }
}
//--------------------------------------
// 閉包

interface T2_Closure<T, E> {

    public E callback(T in);
}
//--------------------------------------

class T2_Query {

    String name = "xyz";

    void query(T2_Closure closure) {

        Thread th = new Thread(() -> {

            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                out.println(e);
            }
            closure.callback(T2_Query.this);
        });

        th.start();
      
        out.println("thread start");
    }
}

java library

https://stleary.github.io/JSON-java/

https://github.com/stleary

java callback

/**
 *
 * @author xman
 */
public class Tt {

    String name = "......";

    void query(Tool t) {
        t.set(this);
    }

    public static void main(String[] args) {
        Tt tt = new Tt();

        tt.query(new Tool<Tt>() {
            public void set(Tt o) {
                out.println(o.name);
            }
        });

        tt.query((o) -> {
            // error
            out.println(o.name);
        });
    }
}

interface Tool<T> {

    public void set(T in);
}

java 非同步呼叫 callback

public class Ajax_1 {

    Callback callback;

    String name;

    void query(Callback callback) {
        this.callback = callback;
      
        // 非同步
        Thread t = new Thread(() -> {
           
            // 取得查詢
            String name = (new SyncSqlQuery()).query();
            Ajax_1.this.name = name;
            Ajax_1.this.callback.callback();
        });

        t.start();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Ajax_1 a = new Ajax_1();
        int x = 5;
       
        a.query(() -> {
            // 及時命令
            out.println(a.name);
        });
       
       
        a.query(new Callback(){
            public void callback(){
                // 及時命令
                out.println(a.name);
            }
        });

    }

}
//-------------------------------------------------------

public interface Callback {
    void callback();
}
//-------------------------------------------------------
public class SyncSqlQuery {
    public static int id = 0;
   
    String query(){
       
        return "SyncSqlQuery_" + id++;
    }
}
//////////////////////////////////////////////////////////////////////////

/**
 *
 * @author xman
 */
public class Ajax_1 {

    String name;

    void query(Callback callback) {       

        Thread t = new Thread(() -> {
           
            // 取得查詢
            String name = (new SyncSqlQuery()).query();
            Ajax_1.this.name = name;
        });

        t.start();
        try {
            t.join();
        } catch (InterruptedException ex) {
            out.println(ex);
        }

        callback.callback();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Ajax_1 a = new Ajax_1();
        int x = 5;
       
        a.query(() -> {
            out.println(a.name);
        });
       
       
        a.query(new Callback(){
            public void callback(){
                out.println(a.name);
            }
        });
    }
}

java inner-class 閉包

// 運用 innerClass

public class T_4 {

    String name;

    String getName() {
        return name;
    }
    //----------------------------
    class A {
        public void setName(String name) {
            T_4.this.name = name;
        }
    }
    //----------------------------
    public static void main(String[] args) {
        T_4 t = new T_4();
        T_4.A a = t.new A();

        a.setName("Xman");
        out.println(t.getName());
    }
}
/////////////////////////////////////////////////////////////////////////////////////////////
// 運用 lambda
// 比較方便偷懶

interface Callback {
    // callback 內容隨你寫....讚
    public void callback(String name);
}
//-------------------------------------------
public class T_4 {

    String name;

    String getName() {
        return name;
    }

    // 送出一個 callback
    // 來設定 name
    Callback getCallback() {

        // lambda 生成一個 匿名 class implements Callback
        return ((name) -> {
            T_4.this.name = name;
        });
    }

    // ----------------------------
    public static void main(String[] args) {
        T_4 t = new T_4();

        // 藉由 callback 設定 t
        t.getCallback().callback("Xyz");

        out.println(t.getName());
    }
}

java繼承 與變數型態 間的問題

public class T_1 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        T_1_B b = new T_1_B();
        b.showName();

        T_1_A a = b;

        a.showName();

        try {
            a.getName(); // error
        } catch (Exception e) {
            out.println(e);
        }

    }
}
//--------------------------------
class T_1_A {

    String name = "G";

    void showName() {
        out.printf("A(%s)\n", name);
    }
}
//--------------------------------
class T_1_B extends T_1_A {

    void showName() {
        String _name = this.getName();
        out.printf("B(%s)\n", name);
    }

    String getName() {
        return name;
    }
}

Java中對象的類型判斷

Java中對象的類型判斷


instanceof

判斷一個對象是否是一個類的實例，用Java中自帶的關鍵字instanceof似乎可以做到(僅從關鍵字名稱上可以猜測出)，如下面的代碼：

public static void main(String args[]) {
    Object i = new Integer(7);
    if (i instanceof Number) {
        System.out.println("Integer i is a Number");
    } else {
        System.out.println("Integer i isn't a Number");
    }

    if (i instanceof Serializable) {
        System.out.println("Integer i is a Serializable");
    } else {
        System.out.println("Integer i isn't a Serializable");
    }

    if (i instanceof Integer) {
        System.out.println("Integer i is an Integer");
    } else {
        System.out.println("Integer i isn't an Integer");
    }

    if (i instanceof Float) {
        System.out.println("Integer i is a Float");
    } else {
        System.out.println("Integer i isn't a Float");
    }
}



類定義部分為：

public abstract class Number implements java.io.Serializable {}
public final class Integer extends Number implements Comparable<Integer> {}


運行結果：

    Console Output :
    Integer i is a Number
    Integer i is a Serializable
    Integer i is an Integer
    Integer i isn't a Float

然而好像和預期的不太一樣，能看出，使用該關鍵字不僅可以判斷對象是否是某個類的實例，甚至連該類繼承的基類和實現的接口也都能夠被識別為true，雖然這樣在邏輯上沒有任何問題，是可以把Integer當做一個Number來看來用，也當做一個Serializable來看來用，但是這樣返回的結果就沒有針對性了，太過於模糊，我們如果僅僅需要i instanceof Integer為true該怎麼做呢？
Class.equals

還好在Java有一個叫做Class的類，這是一個用來描述類信息的類，我們如果要精確判斷一個對象是否是具體的一個類的實例，可以這麼做：

public static void main(String args[]) {
    Object i = new Integer(7);
    if (i.getClass().equals(Number.class)) {
        System.out.println("Integer i is a Number");
    } else {
        System.out.println("Integer i isn't a Number");
    }

    if (i.getClass().equals(Serializable.class)) {
        System.out.println("Integer i is a Serializable");
    } else {
        System.out.println("Integer i isn't a Serializable");
    }

    if (i.getClass().equals(Integer.class)) {
        System.out.println("Integer i is an Integer");
    } else {
        System.out.println("Integer i isn't an Integer");
    }

    if (i.getClass().equals(Float.class)) {
        System.out.println("Integer i is a Float");
    } else {
        System.out.println("Integer i isn't a Float");
    }
}

java 區域變數的問題

int[] d = {5, 10, 60};

        int[] t = new int[1];
        int y; // 會有問題
       
        for (int i = 0; i < d.length; i++) {
            t[0] = d[i];
            y = d[i];
        }
       
        System.out.println("(%d, %d)",t[0], y);