java中下面这段代码怎么理解？

Question

class Connection {
private static int count = 0;
private int i = 0;
private Connection() { System.out.println("Connection()");}
// Allow creation via static method:
static Connection makeConnection() {
    count++;
    return new Connection();
}
public static int howMany() { return count; } 
public String toString() {
    return ("Connection " + count);
}
}

public class ConnectionManager {
static int howManyLeft = 3;
static Connection[] ca = new Connection[3]; 
{
for(Connection x : ca)   这个非静态代码块怎么理解？
    x = Connection.makeConnection();
}
public static Connection getConnection() {
    if(howManyLeft > 0)
        return ca[--howManyLeft];
    else {
        System.out.println("No more connections");
        return null;
    }
}
public static void main(String[] agrs) {        
    ConnectionManager cm = new ConnectionManager();
    System.out.println(cm.howManyLeft);
    cm.getConnection();
    System.out.println(howManyLeft);
    cm.getConnection();
    System.out.println(howManyLeft);
    cm.getConnection();
    System.out.println(cm.getConnection());
    System.out.println(howManyLeft);

}                   
} 

Answer 1

  因为你的main方法还没调用的时候，类加载的时候已经执行了静态代码块，完成了三次创建对象的操作即连续调用了三次new Connection()操作，所以先打印了三次Connection()。然后执行main方法的时候，你又依次打印System.out.println(howManyLeft);打印剩余的connection个数。你可以注释掉ConnectionManager cm = new ConnectionManager();以后的代码，就可以看到静态代码的执行是加载类的时候，也会打印三次Connection()字符串的。