如何使主线程等待所有线程完成

我有一个程序，其中创建了10个线程来运行。我希望主线程能够等到一切都完成之后再完成。我正在尝试使用.join命令，但它似乎不起作用。另外，我正在尝试显示所有线程的运行时，但是运行不正常。下面是我的代码。

//File: CohanThread.java
//Author: Ryan A. Cohan
//Date: August 4, 2016
//Purpose: To create, run, and analyze a thread based program. IOBound runs IO intensive
//operations in the form of printing 1000 times to the console. CPUBound runs CPU
//intensive operations by computing an equation and printing 1000 times.

package cohanthread;

import java.text.*;

public class CohanThread{

    public static void main(String args[]) throws InterruptedException{
        NumberFormat formatter = new DecimalFormat("#0.00000");

        IOBound io1 = new IOBound();
        IOBound io2 = new IOBound();
        IOBound io3 = new IOBound();
        IOBound io4 = new IOBound();
        IOBound io5 = new IOBound();

        CPUBound cpu1 = new CPUBound();
        CPUBound cpu2 = new CPUBound();
        CPUBound cpu3 = new CPUBound();
        CPUBound cpu4 = new CPUBound();
        CPUBound cpu5 = new CPUBound();

        long scheduleStart = System.currentTimeMillis();
        io1.start();
        io2.join();
        io3.join();
        io4.join();
        io5.join();
        cpu1.join();
        cpu2.join();
        cpu3.join();
        cpu4.join();
        cpu5.join();
        long scheduleEnd = System.currentTimeMillis();
        System.out.println("Runtime of all threads: " + formatter.format((scheduleEnd - scheduleStart) / 1000d));
        System.out.println("Processes complete.");
    }
}

class IOBound extends Thread{
    NumberFormat formatter = new DecimalFormat("#0.00000");
    @Override
    public void run(){
        long start = System.currentTimeMillis();
        for(int i = 0; i < 1000; i++){
            System.out.println("Thread number is: " + i);
        }
        long end = System.currentTimeMillis();
        System.out.println("IO Thread runtime: " + formatter.format((end - start) / 1000d));
    }
}

class CPUBound extends Thread{
    NumberFormat formatter = new DecimalFormat("#0.00000");
    @Override
    public void run(){
        String binary = "";
        long start = System.currentTimeMillis();
        for(int i = 0; i < 1000; i++){
            while(i > 0){
                int remainder = i % 2;
                binary = remainder + binary;
                i = i / 2;
            }
            System.out.println("Binary number: " + binary);
            long end = System.currentTimeMillis();
            System.out.println("CPU Thread runtime: " + formatter.format((end - start) / 1000d));
        }
    }
}