构造方法-空参-有参-私有化-args[]-恶汉式；

---

package com.dengbaobao;
public class Barry$June_person {
    public static void main(String args[]) {
        new Person();
        new Person();
        new Person();
        new Person();
        new Person();
        
    }
}
    class Person{
        private String name;
        private static  int count;
        public Person() {
            count++;
            System.out.println("产生了" + count +"个实例化对象。 ");
        }
        public String getInfo() {
            return "姓名： " + this.name;
        }
    }

---

---

package com.baidu;

public class June$1 {

    public static void main(String[] args) {
        System.out.println(new Person().getInfo());
        System.out.println(new Person("A").getInfo());
        System.out.println(new Person("B").getInfo());
        System.out.println(new Person().getInfo());

    }
}
    class Person{
        private String name;
        private static int count;
        public Person() {
            count++;
            this.name = "NONAME - "+ count ;
        }
        public Person(String name) {
            this.name=name;
            
        }
        public String getInfo() {
            return "姓名： "+ this.name;
            }
    }

---

---

package com.baidu;
public class June$2 {
    public static void main(String args[]) {
        Single s = null;
        s = Single.getInstance();
        s.print();
    }

}
    class Single{
        private static Single instance = new Single();
        private Single() {
            
        }
        public static Single getInstance() {
            return instance;
        }
        public void print() {
            System.out.println("hello world!!!");
        }
    }

---

---

package com.bai;
public class June$3 {
    public static void main(String[] args) {
        Persona per1 = new Persona("张三",30);
        Persona per2 = new Persona("李四",31);
        Persona per3 = new Persona("张五",32);
        System.out.println("---------------------信息修改之前-----------------------------");
        System.out.println(per1.getInfo());
        System.out.println(per1.getInfo());
        System.out.println(per1.getInfo());
        System.out.println("---------------------信息修改之后-----------------------------");
        Persona.city = "B城";
        System.out.println(per1.getInfo());
        System.out.println(per1.getInfo());
        System.out.println(per1.getInfo());
    }

}
class Persona{
    private String name;
    private int age;
    static String city = "A城";
    public Persona(String name,int age) {
        this.name = name;
        this.age = age;
    }
    public String getInfo() {
        return " 姓名："+ this.name + ",年龄：" + this.age + ", 城市： "+city;
    }
}

---

---

package com.bai;
public class StaticDemo {
    public static void main(String args[]) {
        for (int x = 0; x < args.length; x++) {
            System.out.println(args[x] +" . ");
        }

    }

}

---

---

package com.bai;
public class Ehanshi {
        public static void main(String[] args) {
            Ehanshi s=Ehanshi.getSinglePerson();
            System.out.println(s.toString());//得到唯一的对象
        }

    private String name="The God";
    private int age=10000;
    private static Ehanshi  person=new Ehanshi();//生成对象放在java静态池中，否则如果非静态在堆中，生命周期比类短
    private Ehanshi() {};//构造方法私有化可以避免大量实例化对象而消耗内存
    public static Ehanshi getSinglePerson() {//静态方法类外部可以通过类名.获取
        return person;
    }
    @Override
    public String toString() {
        return "SinglePerson [name=" + name + ", age=" + age + "]";
    }

}