public abstract class ClassLoadingTest {

    public static void main(String[] args) {
        User user3 = new User();
        
    }
}

public class User {

    public static User user= new User("wang",18);
    
    public static void userSay(){
        System.out.println("调用userSay静态方法");
        user.say();
    }
    
    static{
        User.userSay();
        System.out.println("进入静态构造代码块");
        User user2333 = new User("wang2333", 19);
        user2333.say();
        user.say();
    }
    
    {
        System.out.println("进入代码块");
    }
    
    private String name;
    private int age;
    
    public User() {}
    public User(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
    public void say(){
        System.out.println(this.getName() + "调用say方法");
    }
    
}

执行结果：
进入代码块
调用userSay静态方法
wang调用say方法
进入静态构造代码块
进入代码块
wang2333调用say方法
wang调用say方法
进入代码块