常见的cmd命令
类 class
字面量
数据类型
输入
public static void main(String[] args) {Scanner a=new Scanner(System.in);int n=a.nextInt();int m=a.nextInt();System.out.println(m+n);}
}算数运算符
package wclg;public class test {public static void main(String[] args) {System.out.println("123"+123);System.out.println(1+99+"武昌理工");}
}
符合运算符隐藏了强制类型转换
逻辑运算符
短路运算符
&& || 和& | 结果一样,只不过效率高
原反补
循环判断
Switch jdk12以上的特性
import java.util.Scanner;public class day4 {public static void main(String[] args) {Scanner sc=new Scanner(System.in);int n=sc.nextInt();switch (n) {case 1 -> {System.out.println("一");}case 2 -> {System.out.println("二");}case 3 -> {System.out.println("三");}default -> {System.out.println("没有这种选项");}}}
}获取随机数
猜数字小游戏
package tets;import java.util.Random;
import java.util.Scanner;public class Test7 {public static void main(String[] args) {Random rand = new Random();int n = rand.nextInt(100)+1;while(true){Scanner sc = new Scanner(System.in);int m=sc.nextInt();if(n==m){System.out.println("猜对了");break;}else if(m>n){System.out.println("猜大了");}else {System.out.println("猜小了");}}}
}
数组
流行的写法
数组的长度是 数组.length
数组名.fori
动态数组初始化
public class Test5 {public static void main(String[] args) {int [] arr =new int [5];for(int i=0;i<arr.length;i++){Scanner sc=new Scanner(System.in);arr[i]=sc.nextInt();}for (int i = 0; i < arr.length; i++) {System.out.printf("%d ", arr[i]);}}
}
整型数组未初始化默认为0
打乱数组元素,随机交换元素
package wclg;import java.util.Random;public class class_61 {public static void main(String[] args) {int []arr={1,2,3,4,5};Random r = new Random();for (int i = 0; i < arr.length; i++) { int num = r.nextInt(arr.length);int tmp = arr[num];arr[num] = arr[i];arr[i] = tmp;}for (int i = 0; i < arr.length; i++) {System.out.printf("%d ", arr[i]);}}
}
数组的内存分配
arr2 存的是arr1的地址,通过arr1的地址内容打印出相应的值
修改arr2的值,相当于通过arr2修改了所指的地址内容值
二维数组
方法
方法是程序中最小的执行单元
也就相当于c语言的函数
重载
重载顾名思义就是方法名相同，参数不同，编译器会根据参数不同调用相应的方法
import java.util.Scanner;public class class_64 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int a = sc.nextInt();int b = sc.nextInt();int c = sc.nextInt();int sum1=Add(a,b);System.out.println(sum1);int sum2=Add(a,b,c);System.out.println(sum2);}public static int Add(int a,int b){return a+b;}public static int Add(int a,int b,int c){return a+b+c;}
}
输出语句的认识
方法就是先进后出
引用
引用数据变量其实就是存的是地址值
import java.sql.SQLOutput;
import java.util.Scanner;
public class class_69 {public static void fun1(int []arr){System.out.print("[");for (int i = 0; i < arr.length; i++) {System.out.printf("%d ",arr[i]);if(i<arr.length-1){System.out.print(",");}}System.out.println("]");}public static int fun2(int []arr){int max=arr[0];for (int i = 1; i < arr.length; i++) {if(arr[i]>max){max=arr[i];}}return max;}public static int fun3(int []arr,int n){for (int i = 0; i < arr.length; i++) {if(arr[i]==n){return 1;}}return 0;}public static int[] fun4(int []arr,int from,int to){int []temp=new int[to-from];int j=0;for (int i = from; i < to; i++) {temp[j++]=arr[i];}return temp;}public static void main(String[] args) {int []arr={11,22,33,44,55};fun1(arr);int max=fun2(arr);System.out.println("max:="+max);Scanner sc=new Scanner(System.in);int n=sc.nextInt();int ret=fun3(arr,n);if(ret==1)System.out.println("存在");elseSystem.out.println("不存在");int from=sc.nextInt();int to=sc.nextInt();int []copyArr= fun4(arr,from,to);for (int i = 0; i < copyArr.length; i++) {System.out.printf("%d ",copyArr[i]);}}}
方法的值传递
传基本数据类型的方法.
public class Test1 {public static void main(String[] args) {int number=100;int ret=fun(number);System.out.println(ret);}public static int fun(int number) {number=200;return number;}
}
传引用数据类型
public class Test2 {public static void main(String[] args) {int []arr={1,2,3,4,5};fun(arr);System.out.println(arr[0]);}public static void fun(int []arr){arr[0]=100;}
}
练习
import javax.swing.*;
import java.util.Scanner;public class class_74 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);double score = sc.nextDouble();int month = sc.nextInt();String ret = sc.next();if (month >= 5 && month <= 10) {double m = fun(score, ret,0.9,0.85);System.out.println(m);} else if (month >= 11 && month <= 12 || month >= 1 && month <= 4) {double m = fun(score, ret,0.7,0.65);System.out.println(m);}}public static double fun ( double score, String ret,double a, double b) {if (ret.equals("头等舱"))score *= a;elsescore *= b;return score;}}
ctrl+p看函数参数
ctrl+alt+m自动抽取方法
public class Test2 {public static int is_prime(int i){for (int j = 2; j <=Math.sqrt(i) ; j++) {if(i % j == 0){return 0;}}return 1;}public static void main(String[] args) {int count = 0;for (int i = 101; i <=200; i++) {if(is_prime(i)==1){count++;System.out.printf("%d ", i);}}System.out.println();System.out.println("total:="+count);}
}
import javax.swing.*;
import java.util.Random;
public class Test3 {public static void main(String[] args) {//1.大写字母和小写字母放入数组当中char []arr=new char[52];for (int i = 0; i < arr.length; i++) {if(i<=25) {//添加小写字母arr[i] = (char) (97 + i);}else{//-26之前i的值arr[i] = (char) (65 + i-26);}}//2.随机4次//随机抽取数组的索引//利用随机索引,获取对应的元素//然后4个字母拼接一起Random r=new Random();int j=0;String result="";for (int i = 0; i < 4; i++) {int index=r.nextInt(arr.length);result+=arr[index];}//3.随机抽取一个数字0-9Random c=new Random();int a=c.nextInt(10);//拼接数字result+=a;System.out.println(result);}
}
public class Test4 {public static void main(String[] args) {int []arr = {1,2,3,4,5,6,7,8,9};int []tmp = new int[arr.length];for (int i = 0; i < arr.length; i++) {tmp[i] = arr[i];}for (int i = 0; i < tmp.length; i++) {System.out.printf("%d ", tmp[i]);}}
}
shift+F6一键替换
import java.util.Scanner;
public class Test5 {public static void main(String[] args) {int []newArr=getScore();int max=getMax(newArr);int min=getMin(newArr);int sum=getSum(newArr);int df= (sum-max-min)/4;System.out.println(df);}public static int[] getScore() {int []arr=new int[6];Scanner sc=new Scanner(System.in);for(int i=0;i<6;) {int score=sc.nextInt();if(score>=0 && score<=100) {arr[i]=score;i++;}else{System.out.println("输入成绩错误");}}return arr;}public static int getMax(int[] arr) {int max=arr[0];for (int i = 0; i < arr.length; i++) {if(max<arr[i]) {max=arr[i];}}return max;}public static int getMin(int[] arr) {int min=arr[0];for (int i = 0; i < arr.length; i++) {if(min>arr[i]) {min=arr[i];}}return min;}public static int getSum(int[] arr) {int sum=0;for (int i = 0; i < arr.length; i++) {sum+=arr[i];}return sum;}
}
import javax.swing.*;
import java.util.Scanner;
public class Test6 {public static void main(String[] args) {int n = 0;Scanner sc = new Scanner(System.in);n = sc.nextInt();int count = 0;int tmp=n;while (tmp != 0) {count++;tmp/=10;}int ret = fun(n,count);System.out.println(ret);}public static int fun(int n, int count){int []arr = new int[count];int i=arr.length-1;while(n!=0){arr[i--]=n%10;n/=10;}for ( int j = 0;j <count; j++) {arr[j]+=5;arr[j]%=10;}int left=0;int right=count-1;while(left<right){int tmp=arr[left];arr[left]=arr[right];arr[right]=tmp;left++;right--;}int number=0;for (int k = 0; k < count; k++) {number=number*10+arr[k];}return number;}
}
import java.util.Random;
public class Tets8 {public static void main(String[] args) {int[]arr={2,588,888,1000,10000};int[] newAarr=new int[arr.length];Random random=new Random();for(int i=0;i<5;){int index=random.nextInt(arr.length);int ret=arr[index];if((fun(newAarr,ret))==0){newAarr[i++]=ret;}}for(int i=0;i<arr.length;i++){System.out.print(newAarr[i]+" ");}}public static int fun(int[] arr,int ret){for(int i=0;i<arr.length;i++){if(arr[i]==ret)return 1;}return 0;}
}
方法2
import java.util.Random;public class Test9 {public static void main(String[] args) {int []arr= {2, 588, 888, 1000, 10000};int []newArr=new int[arr.length];Random myRandom=new Random();for(int i=0;i<arr.length;i++){int index=myRandom.nextInt(arr.length);int temp=arr[index];arr[index]=arr[i];arr[i]=temp;}for(int i=0;i<arr.length;i++){System.out.print(arr[i]+" ");}}
}
import java.util.Random;
import java.util.Scanner;public class Test1 {public static void main(String[] args) {//1.生成中奖号码int[] arr = fun1();//123456 7//2.用户输入号码(红球+蓝球)int[] newarr = fun2();//654321 7 也算，只要存在即可//3.判断用户中奖情况int readcount=0;int bluecount=0;//判断红球for (int i = 0; i < newarr.length-1; i++) {int readnum= newarr[i];for (int j = 0; j < arr.length-1; j++) {if(readnum==arr[j]){readcount++;break;}}}//判断蓝球int bluednum= newarr[newarr.length-1];if(bluednum==arr[arr.length-1]){bluecount++;}}public static int[] fun2() {//用于用户购买的彩票号码int[] arr = new int[7];Scanner sc = new Scanner(System.in);for (int i = 0; i < 6; ) {System.out.println("请输入第" + (i + 1) + "个红球号码");int readnum = sc.nextInt();//要求红球在1-33之间,并且不重复才添加数组里面if (readnum >= 1 && readnum <= 33) {int flag = contains(arr, readnum);if (flag == 0) {arr[i] = readnum;i++;} else {System.out.println("重复,请重新输入 ");}} else {System.out.println("当前红球超出范围");}}System.out.println("输入蓝球号码");while (true) {int bluenum = sc.nextInt();if (bluenum >= 1 && bluenum <= 16) {arr[arr.length - 1] = bluenum;break;} else {System.out.println("蓝球号码超出范围请重新输入");}}return arr;}public static int[] fun1() {// 1.6个红球,一个蓝球//红球不能重复,蓝球可以重复int[] arr = new int[7];Random r = new Random();for (int i = 0; i < 6; ) {//获取红球号码int readNum = r.nextInt(33) + 1;int flag = contains(arr, readNum);//保证红球不重复if (flag == 0) {arr[i] = readNum;i++;}}//获取蓝球号码//最后一个蓝球号码int bluenum = r.nextInt(16) + 1;arr[arr.length - 1] = bluenum;return arr;}public static int contains(int[] arr, int Num) {for (int i = 0; i < arr.length; i++) {if (arr[i] == Num) {return 1;}}return 0;}
}
面向对象
封装,继承,多态,面向对象的三大特性
面向对象就是找到对应的方法解决对应的问题
类和对象
不写main方法的类
默认初始化值
'
封装
比如人画圆, 画圆的方法属于圆的方法
对象代表什么,就得封装对应的数据,并提供数据对应的行为
private关键字
set修改成员变量的值
get是获取成员变量的值
import java.util.Set;public class GirlFriend {private String name;private int age;//针对于每一个私有化成员变量,都要有Get和set方法//set类方法:给成员变量赋值//get类方法:对外提供成员变量的值//作用:给成员变量name进行赋值public void Set_name (String n){name = n;}//对外提供name属性的public String Get_name (){return name;}//作用:给成员变量age进行赋值public void Set_age (int a){if(a>=18 && a<=25){age=a;}else {System.out.println("非法参数");}}//对外提供age属性的public int Get_age (){return age;}public void Sleep() {System.out.println("她在睡觉");}public void eat() {System.out.println("她在吃饭");}
}public class GirlFriendTest {public static void main(String[] args) {GirlFriend g = new GirlFriend();g.Set_name("小囧囧");g.Set_age(19);System.out.println(g.Get_name());System.out.println(g.Get_age());g.Sleep();g.eat();} }
this 关键字
成员和局部变量
加this就使用成员变量的age 也就是 private 的age
public class Test2 {private int age;public void method(){int age=10;System.out.println(this.age);}
}
public class Tets1 {public static void main(String[] args) {Test2 t2=new Test2();t2.method();}
}
this的内存布局
this的本质是: 所在方法调用者的地址值
public class GirlFriendTest {public static void main(String[] args) {GirlFriend g = new GirlFriend();g.Set_name("小囧囧");g.Set_age(19);System.out.println(g.Get_name());System.out.println(g.Get_age());g.Sleep();g.eat();}
}
import java.util.Set;public class GirlFriend {private String name;private int age;//针对于每一个私有化成员变量,都要有Get和set方法//set类方法:给成员变量赋值//get类方法:对外提供成员变量的值//作用:给成员变量name进行赋值public void Set_name (String name){this.name = name;}//对外提供name属性的public String Get_name (){return name;}//作用:给成员变量age进行赋值public void Set_age (int age){if(age>=18 && age<=25){this.age = age;}else {System.out.println("非法参数");}}//对外提供age属性的public int Get_age (){return age;}public void Sleep() {System.out.println("她在睡觉");}public void eat() {System.out.println("她在吃饭");}
}
构造
创造对象的时候 ,虚拟机会自动调用构造方法,作用是给成员变量进行初始化
有参构造和空参构造
构造就是public加类名
public class Student {//如果我们自己没有任何的构造方法//那么虚拟机给我们加一个空参构造方法private String name;private int age;public Student(){System.out.println("看看我执行没有");}public Student(String name, int age){this.name = name;this.age = age;}public void setName(String name){this.name = name;}public String getName(){return name;}public void setAge(int age){this.age = age;}public int getAge(){return age;}
}
public class StudentTest {public static void main(String[] args) {//创建对象//调用空参构造Student s = new Student("zhangsan",18);/* s.setAge(18);s.setName("小囧囧");*/System.out.println(s.getAge());System.out.println(s.getName());}
}
如果我们需要键盘录入数据则使用空参构造最好
如果我们给数据使用有参构造最好
不同情况使用不同构造方法
标准javabean类型
下载插件ptg一键生成Javabean类型
这个也可以 点构造函数即可
package Test3;public class User {private String username;private String password;private String email;private String gender;private int age;public User() {}public User(String username, String password, String email, String gender, int age) {this.username = username;this.password = password;this.email = email;this.gender = gender;this.age = age;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public String getGender() {return gender;}public void setGender(String gender) {this.gender = gender;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String toString() {return "User{username = " + username + ", password = " + password + ", email = " + email + ", gender = " + gender + ", age = " + age + "}";}
}
package Test3;public class UserTest {public static void main(String[] args) {User u=new User("张三","123","666@qq.com","男",18);System.out.println(u);}
}
二个引用指向同一个对象
基本数据类型和引用数据类型
基本数据类型存的是真实值
引用数据类型存的是地址值
成员变量和局部变量区别
面向对象练习
练习1
第一版程序
在这段代码中，this.getName()和 role.getName()都是用来访问对象的方法。
-
this.getName()表示调用attack方法的对象（即攻击者）的名字。在Java中，关键字this代表当前对象的引用，所以this.getName()表示调用当前对象的getName()方法，获取当前对象的名字。
-
role.getName()表示被攻击的对象（即参数中的role）的名字。在Java中，role是attack方法的参数，它是一个Role类型的对象，在这个对象上调用getName()方法，获取被攻击对象的名字。
在这段代码中，Role不是数据类型，而是一个类名。在面向对象的编程中，类是用来描述具有相似属性和行为的对象的模板。在这里，Role类描述了角色的属性（如名字和血量）以及行为（如攻击）。在attack方法中，Role role表示传入的参数是一个Role类的实例，即被攻击的角色是一个Role类型的对象。
import java.util.Random;public class Role {private String name;private int blood;public Role() {}public Role(String name, int blood) {this.name = name;this.blood = blood;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getBlood() {return blood;}public void setBlood(int blood) {this.blood = blood;}/*定义一个方法用于攻击别人谁攻击谁Role r1=new Role();Role r2=new Role();r1.攻击(r2)方法的调用者攻击参数*/public void attack(Role role) {//计算造成的伤害1~20Random num = new Random();int hurt=num.nextInt(20)+1;//修改一下挨揍人的血量//剩余血量int remainboold=role.getBlood()-hurt;remainboold=remainboold<0?0:remainboold;//修改一下挨揍人的血量role.setBlood(remainboold);System.out.println(this.getName() +"举起拳头打了"+ role.getName()+"一下,造成了"+hurt+"点伤害"+"还剩下"+remainboold+"血量");}}
public class GameTest {public static void main(String[] args) {// 1.创建第一个角色Role r1=new Role("乔峰",100);//2.创建第二个角色Role r2= new Role("鸠摩智",100);//3.开始格斗,回合制游戏while (true){//r1开始攻击r2r1.attack(r2);//判断r2的剩余血量if(r2.getBlood()==0){System.out.println(r1.getName()+"KO了"+r2.getName());break;}//r2攻击r1r1.attack(r2);if(r1.getBlood()==0){System.out.println(r2.getName()+"KO了"+r1.getName());break;}}}
}
优化版
public class GameTest {public static void main(String[] args) {// 1.创建第一个角色Role r1 = new Role("乔峰", 100, '男');//2.创建第二个角色Role r2 = new Role("鸠摩智", 100, '男');//展示一下角色信息r1.showRoleInfo();r2.showRoleInfo();//3.开始格斗,回合制游戏while (true){//r1开始攻击r2r1.attack(r2);//判断r2的剩余血量if(r2.getBlood()==0){System.out.println(r1.getName()+"KO了"+r2.getName());break;}//r2攻击r1r1.attack(r2);if(r1.getBlood()==0){System.out.println(r2.getName()+"KO了"+r1.getName());break;}}}
}
import java.util.Random;public class Role {private String name;private int blood;private char gender;private String face;String[] boyfaces = {"风流俊雅", "气宇轩昂", "相貌英俊", "五官端正", "相貌平平", "一塌糊涂", "面目狰狞"};String[] girlfaces = {"美奂绝伦", "沉鱼落雁", "婷婷玉立", "身材娇好", "相貌平平", "相貌简陋", "惨不忍睹"};// attack 攻击描述：String[] attacks_desc={"%s使出了一招【背心钉】，转到对方的身后，一掌向%s背心的灵台穴拍去。","%s使出了一招【游空探爪】，飞起身形自半空中变掌为抓锁向%s。","%s大喝一声，身形下伏，一招【劈雷坠地】，捶向%s双腿。","%s运气于掌，一瞬间掌心变得血红，一式【掌心雷】，推向%s。","%s阴手翻起阳手跟进，一招【没遮拦】，结结实实的捶向%s。","%s上步抢身，招中套招，一招【劈挂连环】，连环攻向%s。"};// injured 受伤描述：String[] injureds_desc={"结果%s退了半步，毫发无损","结果给%s造成一处瘀伤","结果一击命中，%s痛得弯下腰","结果%s痛苦地闷哼了一声，显然受了点内伤","结果%s摇摇晃晃，一跤摔倒在地","结果%s脸色一下变得惨白，连退了好几步","结果『轰』的一声，%s口中鲜血狂喷而出","结果%s一声惨叫，像滩软泥般塌了下去"};public Role() {}public Role(String name, int blood, char gender) {this.name = name;this.blood = blood;this.gender = gender;//随机长相setFace(gender);}public Role(String name, int blood, char gender, String face, String[] boyfaces, String[] girlfaces) {this.name = name;this.blood = blood;this.gender = gender;this.face = face;this.boyfaces = boyfaces;this.girlfaces = girlfaces;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getBlood() {return blood;}public void setBlood(int blood) {this.blood = blood;}/*定义一个方法用于攻击别人谁攻击谁Role r1=new Role();Role r2=new Role();r1.攻击(r2)方法的调用者攻击参数*/public void attack(Role role) {Random r = new Random();int index = r.nextInt(attacks_desc.length);String KungFu=attacks_desc[index];//输出一个攻击效果System.out.printf(KungFu,this.getName(),role.getName());//计算造成的伤害1~20int hurt = r.nextInt(20) + 1;//修改一下挨揍人的血量//剩余血量int remainboold = role.getBlood() - hurt;remainboold = remainboold < 0 ? 0 : remainboold;//修改一下挨揍人的血量role.setBlood(remainboold);/*受伤的描述血量>90 0索引的描述80~90 1索引的描述70~80 2索引的描述60~70 3索引的描述40~60 4索引的描述20~50 5索引的描述10~20 6索引的描述小于10的 7索引的描述*/if(remainboold >90){System.out.printf(injureds_desc[0],role.getName());}else if(remainboold >80 && remainboold <=90){System.out.printf(injureds_desc[1],role.getName());}else if(remainboold >70 && remainboold <=80){System.out.printf(injureds_desc[2],role.getName());}else if(remainboold >60 && remainboold <=70){System.out.printf(injureds_desc[3],role.getName());}else if(remainboold >40 && remainboold <=60){System.out.printf(injureds_desc[4],role.getName());}else if(remainboold >20 && remainboold <=50){System.out.printf(injureds_desc[5],role.getName());}else if(remainboold >10 && remainboold <=20){System.out.printf(injureds_desc[6],role.getName());}else{System.out.printf(injureds_desc[7],role.getName());}System.out.println();}public char getGender() {return gender;}public void setGender(char gender) {this.gender = gender;}public String getFace() {return face;}public void setFace(char gender) {Random r = new Random();//长相是随机的if (gender == '男') {//从boyfaces里面随机int index = r.nextInt(boyfaces.length);this.face = boyfaces[index];} else if (gender == '女') {//从girlfaces里面随机int index = r.nextInt(girlfaces.length);this.face = girlfaces[index];} else {this.face = "面目狰狞";}}public String[] getBoyfaces() {return boyfaces;}public void setBoyfaces(String[] boyfaces) {this.boyfaces = boyfaces;}public String[] getGirlfaces() {return girlfaces;}public void setGirlfaces(String[] girlfaces) {this.girlfaces = girlfaces;}public void showRoleInfo() {System.out.println("姓名为" + getName());System.out.println("姓别为" + getGender());System.out.println("血量为" + getBlood());System.out.println("颜值为" + getFace());}}
练习2
ctr+p查参数
package Tets;
public class Goods {private String id;private String name;private double price;private int count;public Goods() {}public Goods(String id, String name, double price, int count) {this.id = id;this.name = name;this.price = price;this.count = count;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}public int getCount() {return count;}public void setCount(int count) {this.count = count;}}
package Tets;
public class GoodTest {public static void main(String[] args) {//1.创建一个数组Goods[]arr=new Goods[3];//2.创建3个商品对象Goods g1=new Goods("001","p40",5999.0,100);Goods g2=new Goods("002","p50",6999.0,200);Goods g3=new Goods("003","p60",7999.0,500);//3. 把商品添加到数组中arr[0]=g1;arr[1]=g2;arr[2]=g3;for (int i = 0; i < arr.length; i++) {Goods g=arr[i];System.out.println(g.getId()+","+g.getName()+","+g.getPrice()+","+g.getCount());}}
}
键盘录入
nextLine遇到空格不停止
练习3
string
package com.ithema;
import java.util.Random;
public class StringDemo01 {public static void main(String[] args) {//1.使用直接赋值的方式获取一个字符串对象String s1="abc";System.out.println(s1);//2.使用new的方式来获取一个字符串对象//空参构造:可以获取一个空白字符串对象String s2=new String();System.out.println('*'+s2+'!');//传递一个字符串,根据传递的字符串内容再创建一个新的字符串对象String s3=new String("abc");System.out.println(s3);//传递一个字符数组,根据字符数组的内容再创建一个新的字符串对象//需求:我们修改字符串的内容 abc Qbcchar []arr={'a','b','c'};String s4=new String(arr);System.out.println(s4);//传递一个字节数组,根据字节数组的内容再创建一个新的字符串对象byte []bytes={97,98,99};String s5=new String(bytes);System.out.println(s5);}
}
引用数据类型 s1!=s2 因为new开辟不同的空间
