Java: Instance Creation and Invocation with Runtime Reflection #java #reflection #runtime

AccountWorker.java

package com.ps.utils;

import com.ps.finance.BankAccount;
import com.ps.finance.HighVolumeAccount;

public class AccountWorker implements Runnable {
    private BankAccount ba;
    private HighVolumeAccount hva;
    private char txType = 'w';

    public AccountWorker(BankAccount ba) {
        this.ba = ba;
    }

    public AccountWorker(HighVolumeAccount hva) {
        this.hva = hva;
    }

    public void doWork() {
        // HighVolumeBankAccount already implements Runnable
        Thread t = new Thread(hva != null ? hva : this);
        t.start();
        try {
            t.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void setTxType(char type) {
        this.txType = type;
    }

    @Override
    public void run() {
        int amt = 50;
        if (txType == 'w')
            ba.withdraw(amt);
        else
            ba.deposit(amt);
    }
}

BankAccount.java

package com.ps.finance;

public class BankAccount {
    private String id;
    private int balance;

    public BankAccount(String id) {
        this.id = id;
    }

    public BankAccount(String id, int balance) {
        this.id = id;
        this.balance = balance;
    }

    public String getId() {
        return id;
    }

    public synchronized int getBalance() {
        return balance;
    }

    public synchronized void deposit (int amount) {
        this.balance += amount;
    }

    public synchronized void withdraw (int amount) {
        this.balance -= amount;
    }
}

HighVolumeAccount.java

package com.ps.finance;

public final class HighVolumeAccount extends BankAccount implements Runnable {

    public HighVolumeAccount(String id) { super(id); }
    public HighVolumeAccount(String id, int balance) { super(id, balance); }

    private int[] readDailyDeposits() {
        return new int[100];
    }

    private int[] readDailyWithdrawals() {
        return new int[100];
    }

    @Override
    public void run() {
        for(int depositAmt : readDailyDeposits())
            deposit(depositAmt);

        for(int withdrawalAmt : readDailyWithdrawals())
            withdraw(withdrawalAmt);
    }
}

InstanceCreationAndInvocation.java

package com.ps;

import com.ps.finance.BankAccount;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;

public class InstanceCreationAndInvocation {
    public static void main(String[] args) {
        doWorkOnBankAccount();
    }

    private static void doWorkOnBankAccount() {
        BankAccount acct = new BankAccount("1234");
        startWork("com.ps.utils.AccountWorker", acct);
        System.out.println("New balance is " + acct.getBalance());
    }

    private static void startWork(String workerTypeName, Object workerTarget) {
        try {
            Class<?> workerType = Class.forName(workerTypeName);
            Class<?> targetType = workerTarget.getClass();

            // Get constructor based on the Class parameter you pass to it
            Constructor c = workerType.getConstructor(targetType);
            Object worker = c.newInstance(workerTarget);

            // Get method and invoke
            Method doWork = workerType.getMethod("doWork");
            doWork.invoke(worker);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}