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Java（12）Object类，Optional类，浅拷贝与深拷贝

code • 2022-5-5 • java • 阅读 39

Java（12）Object类，Optional类，浅拷贝与深拷贝,第1张

01 == 与 equals 
package;

public class Person01 {
    private String nickname;
    private int age;
    private int gender;

    public Person01() {
    }

    public Person01(String nickname, int age, int gender) {
        this.nickname = nickname;
        this.age = age;
        this.gender = gender;
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getGender() {
        return gender;
    }

    public void setGender(int gender) {
        this.gender = gender;
    }
}

package Test;

import HashTable;
import Person01;
import org.junit.jupiter.api.Test;

public class Person01Test {
    @Test
    public void test01(){
        int a = 10;
        int b = 10;
        System.out.println(a == b);
        Integer x = 10;
        Integer y = 10;
        System.out.println(x == y);
        System.out.println(x.equals(y));
        Integer aa = 128;
        Integer bb = 128;
        System.out.println(aa == bb);
        System.out.println(aa.equals(bb));
    }
/*
true
true
true
false
true
*/
    @Test
    public void test02(){
        String str01 = new String("abc");
        String str02 = new String("abc");
        System.out.println(str01 == str02);
        System.out.println(str01.equals(str02));
        System.out.println(str01.compareTo(str02));
    }
/*
false
true
0
*/
    @Test
    public void test03(){
        Person01 person01 = new Person01("姓名", 20, 1);
        Person01 person02 = new Person01("姓名", 20, 1);
        System.out.println(person01 == person02);
        System.out.println(person01.equals(person02));
    }
/*
false
false
*/
    @Test
    public void test04(){
        Person01 person01 = new Person01("xm", 20, 1);
        Person01 person02 = new Person01("xm", 20, 1);
        // Person01@dbd940d
        System.out.println(person01);
        // 230528013
        System.out.println(person01.hashCode());
        // dbd940d
        System.out.println(Integer.toHexString(person01.hashCode()));

        // Person01@71d15f18
        System.out.println(person02);
        // 1909546776
        System.out.println(person02.hashCode());
        // 71d15f18
        System.out.println(Integer.toHexString(person02.hashCode()));
    }
/*
Person01@dbd940d
230528013
dbd940d
Day15.Person01@71d15f18
1909546776
71d15f18
*/
    @Test
    public void test05(){
        String[] names = new String[8];
        names[3] = "xm";
        names[6] = "x";
        for (int i = 0; i < names.length; i++) {
            if ("xm".equals(names[i])) {
                System.out.println(names[i]);
                break;
            }
        }
        System.out.println("程序完成");
    }
/*
xm
程序完成
*/
}
02 hash 
    @Test
    public void test06(){
        HashTable hashTable = new HashTable();
        int[] hashcodes = hashTable.getHashcodes();
        hashcodes[33] = 33;
        hashcodes[66] = 66;
        hashTable.setHashcodes(hashcodes);
        String[] values = hashTable.getValues();
        values[33] = "xm";
        values[66] = "x";
        hashTable.setValues(values);
        values = hashTable.getValues();

        System.out.println(values[33]);
        System.out.println(values[66]);
        System.out.println("程序完成");
    }
/*
xm
x
程序完成
*/
03 Object类equals方法和hasecode方法 
package;

public class Person02 {
    private String nickname;
    private int age;
    private int gender;

    public Person02() {
    }

    public Person02(String nickname, int age, int gender) {
        this.nickname = nickname;
        this.age = age;
        this.gender = gender;
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getGender() {
        return gender;
    }

    public void setGender(int gender) {
        this.gender = gender;
    }

    @Override
    public boolean equals(Object o) {
        if (o == null) {
            return false;
        }
        Person02 person02 = (Person02) o;
        if (this.age != person02.getAge()) {
            return false;
        } else if (this.gender != person02.getGender()) {
            return false;
        } else if (!this.nickname.equals(person02.getNickname())) {
            return false;
        } else {
            return true;
        }
    }

    @Override
    public int hashCode() {
        int reference = 31;
        return this.age * (this.gender + reference) + this.nickname.hashCode();
    }
}

package Test;

import Person01;
import Person02;
import org.junit.jupiter.api.Test;

public class Person02Test {
    @Test
    public void test01(){
        Person01 person011 = new Person01("姓名", 20, 1);
        Person01 person012 = new Person01("姓名", 20, 1);
        Person02 person021 = new Person02("姓名", 20, 1);
        Person02 person022 = new Person02("姓名", 20, 1);
        System.out.println(person011.hashCode());
        System.out.println(person012.hashCode());
        System.out.println(person021.hashCode());
        System.out.println(person022.hashCode());
        System.out.println(person011 == person012);
        System.out.println(person011.equals(person012));
        System.out.println(person021 == person022);
        System.out.println(person021.equals(person022));
    }
/*
611563982
1615039080
735002
735002
false
false
false
true
*/
}
04 Object类toString方法 
package;

public class Person03 {
    private String nickname;
    private int age;
    private int gender;

    public Person03() {
    }

    public Person03(String nickname, int age, int gender) {
        this.nickname = nickname;
        this.age = age;
        this.gender = gender;
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getGender() {
        return gender;
    }

    public void setGender(int gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Person03{" +
                "nickname='" + nickname + '\'' +
                ", age=" + age +
                ", gender=" + gender +
                '}';
    }
}


package Test;

import Person03;
import org.junit.jupiter.api.Test;

public class Person03Test {
    @Test
    public void test(){
        Person03 person01 = new Person03("姓名", 20, 1);
        Person03 person02 = new Person03("姓", 29, 1);
        System.out.println(person01.toString());
        System.out.println(person02.toString());
    }
/*
Person03{nickname='姓名', age=20, gender=1}
Person03{nickname='姓', age=29, gender=1}
*/
}
05 浅拷贝与深拷贝 
package;

public class Person04 implements Cloneable{
    private String nickname;

    public Person04() {
    }

    public Person04(String nickname) {
        this.nickname = nickname;
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

package Test;

import Person04;
import org.junit.jupiter.api.Test;

public class Person04Test {
    @Test
    public void test01(){
        Person04 person01 = new Person04("姓名");
        Person04 person02 = person01;
        System.out.println(person01.getNickname());
        System.out.println(person02.getNickname());
        person02.setNickname("姓");
        System.out.println(person01.getNickname());
        System.out.println(person02.getNickname());
    }
    /*
姓名
姓名
姓
姓
     */
    @Test
    public void test02(){
        Person04 person01 = new Person04("姓名");
        Person04 person02 = new Person04(person01.getNickname());
        System.out.println(person01.getNickname());
        System.out.println(person02.getNickname());
        person02.setNickname("姓");
        System.out.println(person01.getNickname());
        System.out.println(person02.getNickname());
    }
    /*
姓名
姓名
姓名
姓
     */
    @Test
    public void test03() throws CloneNotSupportedException {
        Person04 person01 = new Person04("姓名");
        Person04 person02 = (Person04) person01.clone();
        System.out.println(person01.getNickname());
        System.out.println(person02.getNickname());
        person02.setNickname("姓");
        System.out.println(person01.getNickname());
        System.out.println(person02.getNickname());
    }
    /*
姓名
姓名
姓名
姓
     */
}

package;

/**
 * 浅拷贝：指的是你的类本身被拷贝，而没有拷贝类本身属性中的类。
 * 深拷贝：指的是包含类本身和属性类在内的所有类的拷贝。
 */
public class Person05 implements Cloneable {
    private String nickname;
    private Address05 address05;

    public Person05(String 姓名, String 姓) {
    }

    public Person05(String nickname, Address05 address05) {
        this.nickname = nickname;
        this.address05 = address05;
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public Address05 getAddress05() {
        return address05;
    }

    public void setAddress05(Address05 address05) {
        this.address05 = address05;
    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    @Override
    public String toString() {
        return "Person05{" +
                "nickname='" + nickname + '\'' +
                ", address05=" + address05 +
                '}';
    }
}

package Test;

import Address05;
import Person05;
import org.junit.jupiter.api.Test;

public class Person05Test {
    @Test
    public void test01() throws CloneNotSupportedException {
        Person05 person01 = new Person05("姓名", new Address05("名"));
        Person05 person02 = (Person05) person01.clone();
        System.out.println(person01);
        System.out.println(person02);
        person02.setNickname("姓");
        System.out.println(person01);
        System.out.println(person02);
        Address05 address05 = person02.getAddress05();
        address05.setCity("啦啦啦");
        person02.setAddress05(address05);
        System.out.println(person01);
        System.out.println(person02);
    }
    /*
Person05{nickname='姓名', address05=Address05{city='名'}}
Person05{nickname='姓名', address05=Address05{city='名'}}
Person05{nickname='姓名', address05=Address05{city='名'}}
Person05{nickname='姓', address05=Address05{city='名'}}
Person05{nickname='姓名', address05=Address05{city='啦啦啦'}}
Person05{nickname='姓', address05=Address05{city='啦啦啦'}}
     */
}


package;

/**
 * 浅拷贝：指的是你的类本身被拷贝，而没有拷贝类本身属性中的类。
 * 深拷贝：指的是包含类本身和属性类在内的所有类的拷贝。
 */
public class Person06 implements Cloneable {
    private String nickname;
    private Address06 address06;

    public Person06() {
    }

    public Person06(String nickname, Address06 address06) {
        this.nickname = nickname;
        this.address06 = address06;
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public Address06 getAddress06() {
        return address06;
    }

    public void setAddress06(Address06 address06) {
        this.address06 = address06;
    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        return new Person06(this.nickname, (Address06) this.address06.clone());
    }

    @Override
    public String toString() {
        return "Person06{" +
                "nickname='" + nickname + '\'' +
                ", address06=" + address06 +
                '}';
    }
}

package Test;

import Address06;
import Person06;
import org.junit.jupiter.api.Test;

public class Person06Test {
    @Test
    public void test01() throws CloneNotSupportedException {
        Person06 person01 = new Person06("姓名", new Address06("名"));
        Person06 person02 = (Person06) person01.clone();
        System.out.println(person01);
        System.out.println(person02);
        person02.setNickname("姓");
        System.out.println(person01);
        System.out.println(person02);
        Address06 address06 = person02.getAddress06();
        address06.setCity("啦啦啦");
        person02.setAddress06(address06);
        System.out.println(person01);
        System.out.println(person02);
    }
    /*
Person06{nickname='姓名', address06=Address06{city='名'}}
Person06{nickname='姓名', address06=Address06{city='名'}}
Person06{nickname='姓名', address06=Address06{city='名'}}
Person06{nickname='姓', address06=Address06{city='名'}}
Person06{nickname='姓名', address06=Address06{city='名'}}
Person06{nickname='姓', address06=Address06{city='啦啦啦'}}
     */
}

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原文地址: http://outofmemory.cn/langs/788251.html

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