java中Object类中一些方法的练习

浅浅的花香味﹌ 2022-07-16 12:49 133阅读 0赞

类Object是类层次结构的根类。每个类都使用Object类作为超类（extends Object）。所有对象（包括数组）都实现这个类。  
成员方法：  
public int hashCode();  
public final Class getClass();  
public String toString();  
public boolean equals(Object obj);  
protected ovid finalized();  
protected Object clone();  
代码包括三个类，Student类，Teacher类和StudentDemo类。  
Student.java

package cn.day11_Object.test01;
    
    public class Student {
        
        private String name;
        private int age;
        public Student() {
            // TODO Auto-generated constructor stub
        }
        public Student(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 study(){
            System.out.println("学习.");
        }
    
        @Override
        public String toString() {
            //重写了toString()方法，可用alt + shift + s 调出source，
            //然后点击Generate toString()方法
            return "Student [name=" + name + ", age=" + age + "]";
        }
    
        @Override
        public boolean equals(Object obj) {
            if (this == obj)//两者指向同一个对象
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            Student other = (Student) obj;
            if (age != other.age)
                return false;
            if (name == null) {
                if (other.name != null)
                    return false;
            } else if (!name.equals(other.name))
                return false;
            return true;
        }
    
    
    
    /*  @Override
        public boolean equals(Object obj) {
            // TODO Auto-generated method stub
            //判断obj是否是此类对象
            if(!(obj instanceof Student)){
                return false;
            }
    
            Student temp = (Student)obj;
    
            if (this.name.equals(temp) && this.age == temp.age) {
                return true;
            } else {
                return false;
            }
    
    
    
            //直接返回值
            return this.name.equals(temp.name) && this.age == temp.age;
    
    
            if(this.name.equals(temp.name) && this.age == temp.age){
                return true;
            }
            else{
                return false;
            }
    
    
    //      return super.equals(obj);
        }
        */
    }

Teacher.java

package cn.day11_Object.test01;
    
    //导包的快捷键ctrl + shift + o
    import java.util.Date;
    
    public class Teacher implements Cloneable{
        
        private String name;
        private int age;
        private Date time = new Date();
        public Teacher() {
            // TODO Auto-generated constructor stub
        }
        public Teacher(String name, int age, Date time) {
            super();
            this.name = name;
            this.age = age;
            this.time = time;
        }
        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 Date getTime() {
            return time;
        }
        public void setTime(Date time) {
            this.time = time;
        }
        public void teach(){
            System.out.println("老师教学。");
        }
    
        //重写clone()方法
    /*  @Override
        protected Object clone() throws CloneNotSupportedException {
            // TODO Auto-generated method stub
            return super.clone();
        }
        */
    
        public Object clone(){
            Teacher obj = null;
            try {
                obj = (Teacher)super.clone();
            } catch (CloneNotSupportedException e) {
                // TODO: handle exception
                e.printStackTrace();
            }
            obj.time = (Date)this.getTime().clone();
            return obj;
        }
    }

StudentDemo.java

package cn.day11_Object.test01;
    
    import java.util.Date;
    
    public class StudentDemo extends Object{
        public static void main(String[] args) throws CloneNotSupportedException {
            //show1();
            //show2();
            //show3();
            //show4();
            //show5();
            //show6();
            Date b = new Date();
            System.out.println(b);
            show7(b);
    
        }
    
        public static void show7(Date b) throws CloneNotSupportedException{
            /**
             * clone()方法，同样存在浅复制和深复制，
             * 当类中只有基本类型的数据时，用浅复制即可，
             * 当存在非基本类型（引用类型）时，必须对非基本类型的属性也调用clone()方法，
             * 这样才能完成深复制.
             * obj.brith = (Date)this.getBrith().clone();
             */
    
            Teacher t1 = new Teacher("wang", 20, b);
            System.out.println(t1.getName() + "---" + t1.getAge() + "---" + t1.getTime());
            Teacher t2 = (Teacher)t1.clone();
            System.out.println(t2.getName() + "---" + t2.getAge() + "---" + t2.getTime());
        }
    
        public static void show6(){
            Student s1 = new Student("zhang", 32);
            Student s2 = new Student("wang", 22);
            Student s3 = s1;
            System.out.println("重写了equals()方法");
            System.out.println(s1.equals(s2));
            System.out.println(s1.equals(s3));
            System.out.println("-------------------");
            Teacher t1 = new Teacher();
            System.out.println(s1.equals(t1));
        }
    
        public static void show5() {
            Student s1 = new Student();
            Student s2 = new Student();
            Student s3 = s1;
            System.out.println("equals()的特点");
            System.out.println("自反性: " + s1.equals(s1));
            System.out.println(s1.equals(s2));
            System.out.println(s1.equals(s3));
    
        }
    
        public static void show4(){
            // == 判断基本类型的值是否相等。
            int aValue = 3;
            int bValue = 5;
            int cValue = 3;
            boolean bool = aValue == bValue;
            System.out.println(bool);
            System.out.println(aValue == cValue);
            System.out.println("---------------");
            String s1 = "hello";
            String s2 = "world";
            String s3 = "hello";
            boolean b2 = s1 == s2;
            System.out.println(b2);
            System.out.println(s1==s3);
            System.out.println("---------------");
            //Object类的equals()方法
            //Student s = new Student();
    
        }
    
        public static void show3(){
            Student s = new Student();
            //直接调用对象名和调用对象名.toString()效果一样的。
            System.out.println(s);
            System.out.println(s.toString());
        }
    
        public static void show2(){
            Student s = new Student();
            System.out.println(s.toString());
            System.out.println("---------------");
            System.out.println(s.getClass());
            System.out.println(s.getClass().getName());
            System.out.println("---------------");
            System.out.println(s.hashCode());
            System.out.println(s.getClass().getName() + '@' 
                    + Integer.toHexString(s.hashCode()));
        }
    
        public static void show1(){
            //对Objectde getClass()和getName(),toString()的练习。
            Student s1 = new Student();
            System.out.println(s1.hashCode());
            Student s2 = new Student();
            System.out.println(s2.hashCode());
            Student s3 = s1;
            System.out.println(s3.hashCode());
            System.out.println("-------------------");
            Student s4 = new Student();
            //Class c1 = s4.getClass();
            //String sc1 = c1.getName();
            //System.out.println(sc1);
            System.out.println(s4.hashCode());
            System.out.println("--------------");
            System.out.println(s4.getClass().getName());
            System.out.println("---------------");
            System.out.println(s4.toString());
            System.out.println(s3.toString());
            System.out.println(s2.toString());
            System.out.println(s1.toString());
            System.out.println("----------------");
            System.out.println(s3.getClass().getName());
            System.out.println(s2.getClass().getName());
            System.out.println(s1.equals(s3));
            System.out.println("----");
            System.out.println(s1.equals(s2));
            System.out.println("----------------");
            System.out.println("----------------");
            //重写了toString()方法之后，对象名和对象名.toString()在输出的时候是一样的。
            System.out.println(s1);
            System.out.println(s2);
            System.out.println(s3);
            System.out.println(s4);
        }
    
    
    }