Java学习_day003:运算符

约定不等于承诺〃 2023-07-20 10:43 23阅读 0赞

## 运算符 ##

### 1. 算数运算符:+,-,\*,/,%,++,– ###

#### 1.1 %:取模/取余 ####

System.out.println(5%2);//1,商2余1；
    System.out.println(8%2);//0,整除
    System.out.println(2%6);//2,商0余2

#### 1.2 ++or–：自增一or自减一，可在变量前也可在变量后； ####

**单独使用时，在前在后都一样；  
被使用时，在前在后不一样：a++的值为a，++a的值为a+1**

//单独使用
    int a=5,b=5；
    a++；//a=a+1
    ++b;//b=b+1
    System.out.println(a);//6
    System.out.println(b);//6
    //被使用
    int a=5;
    int b=a++;
    System.out.println(a);//6
    System.out.println(b);//5
    /*int a=5; int b=++a; System.out.println(a);//6 System.out.println(b);//6*/
    int c=5,d=5;//把加号换成减号后再算一次
    System.out.println(c++);//5,5
    System.out.println(c);//6,4
    System.out.peintln(++d);//6，4
    System.out.println(d);//6,4

### 2. 赋值运算符：= ###

#### 2.1 简单赋值运算符：= ####

#### 2.2 拓展赋值运算符：+=，-=，\*=，/=，%= ####

**自带了强转功能**

int a=5
    a+=10;//a=a+10
    System.out.println(a);//15
    a*=2;//a=a*2
    System.out.println(a);//30
    a/=6;//a=a/6
    System.out.println(a);//5
    //常见面试题
    		short s=5;
    		s+=10;//相当于s=(short)(a=10)
    		//s=s+10;//编译错误，s+10为int型，故需要强转。

### 3. 字符串连接运算符:+ ###

若两边为数字，则作加法运算  
如两边出现字符串。则作字符串连接  
![在这里插入图片描述][20200401155702995.png]

System.out.println(10+20+""+30);//"3030"
    	System.out.println(""+10+201+30);//"102030"
    	System.out.println(10+20+30+"");//"60"
    	int age=24;
    	System.out.println("age");//age
    	System.out.println(age);//24
    	System.out.println("age="+age);//age=24
    	System.out.println("我的年龄是"+age);
    	System.out.println("我今年"+age+'岁了');
    	String name="mgs";
    	System.out.println("大家好，我叫"+name);

### 4. 关系运算符：>,<,<=,>=,!=（不等）,==（相等）; ###

要做某事由一个条件控制

关系成立则为true，不成立则为false。

### 5. 逻辑运算符 ###

要做某事由多个条件控制

#### “&&”逻辑与；“||”逻辑或；“！”逻辑非 ####

**“&&” 短路与，都真为真（当出现false时则会发生短路，后面直接不执行了）  
“||” 短路或，有真为真（当出现true时则会发生短路，后面直接不执行了）  
“！”非真为假，非假为真**  
其建立在关系运算的基础之上，其结果也为boolean型  
**&&优先于||；**

### 6. 关系/三目运算符 ###

语法：boolean？数一：数二  
执行过程：计算boolean值，true/false  
如为T则为数一，如为F为数二

int number=5;
    int flag=number>0?1:-1;
    System.out.println(flag);//1

**练习：**

System.out.println(5%2);//1,商2余1；
    		System.out.println(8%2);//0,整数
    		System.out.println(2%6);//2,
    		
    		int a=5,b=5;
    		a++;//a=a+1
    		++b;//b=b+1
    		System.out.println(a);//6
    		System.out.println(b);//6
    		/*5 System.out.println(5%2); * System.out.println(9%3); * System.out.println(2%6); * int a=5,b=5; * a++; * ++b; * System.out.println(a); * System.out.println(b); */
    		/*4 System.out.println(5%2); * System.out.println(8%4); * System.out.println(2%5); * int a=5,b=5; * a++; * ++b; * System.out.println(a); * System.out.println(b); */
    		/*3 System.out.println(6%5); * System.out.println(8%2); * System.out.println(3%5); * int a=6,b=7; * a--; * --b; * System.out.println(a); * System.out.println(b); */
    		/*2 System.out.println(9%4); * System.out.println(4%2); * System.out.println(6%7); * int a=4,b=5; * ++a; * b++; * System,out.println(a); * System.out.println(b); */
    		/*1 System.out.println(6%3); * System.out.println(6%4); * System.out.println(2%9); * int a=6,b=7; * a++; * ++b; * System.out.println(a); * System.out.println(b); */
    		/*0 System.out.println(6%4); * System.out.println(6%2); * Systen.out.println(2%5); * int a=4,b=9; * a++; * ++b; * System.out.println(a); * System.out.println(b); */

int a=5;
    		int b=++a;
    		System.out.println(a);//6
    		System.out.println(b);//6
    		int c=5;
    		int d=c++;
    		System.out.println(c);//6
    		System.out.println(d);//5
    		/*5 int a=5; * int b=++a; * System.out.println(a); * System.out.println(b); * int c=5; * int d=c++; * System.out.println(c); * System.out.println(d); */
    		/*4 int a=5; * int b=++a; * System.out.println(a); * System.out.println(b); * int c=6; * int d=c++; * System.println(c); * System.out.println(d); */
    		/*3 int a=6; * int b=++a; * System.out.println(a); * System.out.println(b); * int c=7; * int d=c++; * System.out.println(c); * System.out.println(d); */
    		/*2 int a=7; * int b=a++; * System.out.println(a); * System.out.println(b); * int c=8; * int d=++c; * System.out.println(c); * System.out.println(d); */
    		/*1 int a=5; * int b=a++; * System.out.println(a); * System.out.println(b); * int c=6; * int d=++c; * System.out.println(c); * System.out.println(d); */

int a=5,b=10,c=5;
    		boolean b1=a>b;
    		System.out.println(b1);//false
    		System.out.println(c<b);//true
    		System.out.println(a>=c);//true
    		System.out.println(a<=b);//true
    		System.out.println(a==c);//true
    		System.out.println(a!=c);//false
    		System.out.println(a+c>b);//false
    		System.out.println(a%2==0);//false
    		System.out.println(b%2==0);//true
    		System.out.println(a++>5);//false
    		System.out.println(a++>5);//true
    		/*5 int a=5,b=10,c=5; * boolean b1=a<b; * System.out.println(b1); * System.out.println(a>b); * System.out.println(a>=b); * System.out.println(c<=b); * System.out.println(c==a); * System.out.println(c!=b); * System.out.println(a+b>c); * System.ot.println(++a>c); */
    		/*4 int a=6,b=10,c=4; * boolean b2=a>c; * System.out.println(b2); * System.out.println(c<a); * System.out.println(c<=b); * System.out.println(a>=c); * System.out.println(a==b); * System.out.println(c!=a); * System.out.println(a+c==b); * System.out.println(++a>c); */
    		/*3 int a=6,b=7,c=8; * boolean b3=a>b; * System.out.printlb(a>c); * System.out.println(c<b); * System.out.println(c>=a); * System.out.println(a<=b); * System.out.peintln(a==b); * System.out.println(c!=b); * System.out.println(a+c>b); * System.out.println(a++>c); */
    		/*2 int a=7,b=8,c=9; * boolean b4=c>b; * System.out.println(b4); * System.out.println(a<c); * System.out.println(a>=c); * System.out.println(c<=b); * System.out.println(a==c); * System.out.println(c!=c); * System.out.println(c+a>b); * System.out.println(++b==c); */
    		/*1 int a=3,b=4,c=5; * boolean b1=c>a; * System.out.println(b1); * System.out.println(a<c); * System.out.println(a>=c); * System.out.println(c<=b); * System.out.println(b==a); * System.out.println(c!=b); * System.out.println(a+b<c); * System.out.println(a++>c); */

int a=5,b=10,c=5;
    		boolean b1=b>=a&&b<c;
    		System.out.println(b1);//true&&false==false
    		System.out.println(c>=b&&b>a);//f&&t==f
    		System.out.println(a==b&&c>b);//f&&f==f
    		System.out.println(b!=c&&a<b);//t&&t==t
    
    		System.out.println(b>=a||b<c);//f||t=t
    		System.out.println(c>=b||b>a);//f||t=t
    		System.out.println(b!=c||a<b);//t||t=t
    		System.out.println(a==b||c>b);//f||f=f
    
    		//boolean b2=!a>b;//！的优先级最高，且只能对T\F否，故出现错误；
    		boolean b2=!(a>b);
    		System.out.println(b2);
    		System.out.println(!(a<b));//!t=f
    		/*5 int a=5,b=10,c=5; * boolean b1=b>=a&&b<c; * System.out.primtln(b1); * System.out.println(b<=c&&b>a); * System.out.println(b==c&&b<a); * System.out.println(a!=c&&c>a); * boolean b2=b<=c||b>a; * System.out.println(b2); * System.out.println(b>=c||b<a); * System.out.println(c==a||b>a); * System.out.println(a!=c||b>c); * boolean b3=!(a>c); * System.out.println(b3); * System.out.println(!(b>=a)); */
    		/*4 int a=5,b=10,c=5; * boolean b1=a<=c&&c>a; * System.out.println(b1); * System.out.println(b>=c&&a>c); * System.out.println(b==a&&c<b); * System.out.println(b!=c&&a<b); * boolean b2=c>=a||c<b; * System.out.println(b2); * System.out.println(b>=a||c<=a); * System.out.println(a==c||c>b); * System.out.println(a!=b||a>b); * boolean b3=!(b>c); * System.out.println(b3); * System.out.println(!(c<a)); */
    		/*3 int a=5,b=10,c=5; * boolean b1=a>=c&&b>=c; * System.out.println(b1); * System.out.println(c>=b&&c<a); * System.out.println(a==c&&c>a); * System.out.println(b!=c&&b>a); * boolean b2=b>=a||c<a; * System.out.println(b2); * System.out.println(b>=a||c<a); * System.out.println(a==c||b>a); * System.out.println(a!=b||c<a); * boolean b3=!(a>c); * System.out.println(b3); * Systen.out.println(!(b<a)); */
    		/*2 int a=5,b=10,c=5; * boolean b1=a>=c&&c<=b; * System.out.println(b1); * System.out.println(b<=a&&c>a); * System.out.println(a==c&&b>a); * System.out.println(c!=b&&a>=c); * boolean b2=b>=a||c<a; * System.out.println(b2); * System.out.println(b<=a||b>c); * System.out.println(c==a||c>a); * System.out.println(b!=a||c<b); * boolean b3=!(a>c); * System.out.println(b3); * System.out.println(!(a>=b)); * */
    		/*1 int a=5,b=10,c=5; * boolean b1=b>=a&&c<a; * System.out.println(b1); * Ssytem.out.peintln(b>=a&&c<a); * System.out.println(c==a&&b<a); * System.out.println(c!=a&&c>=a); * boolean b2=b>=c||c<=a; * System.out.println(b2); * Syetem.out.println(a>=b||c<b); * System.out.println(b==c||c<=a); * System.out.println(c!=a||c>a); * boolean b3=!(a>=c); * System.out.println(b3); * Syetem.out.println(!(a>=b)); */

int a=5,b=10,c=5;
    		boolean b3=a>b&&c++>2;
    		System.out.println(b3);//false
    		System.out.println(c);//5,发生短路 
    		boolean b4=a<b||++c>2;//true
    		System.out.println(b4);
    		System.out.println(c);//5,短路
    		/*5 int a=5,b=10,c=5; * boolean b1=a>b&&c++<6; * System.out.println(b1); * System.out.println(c); * boolean b2=b>c||c++>2; * System.out.println(b2); * System.out.println(c); */
    		/*4 int a=5,b=10,c=5; * boolean b1=a>c&&c++>5; * System.out.println(b1); * System.out.println(c); * boolean b2=b>c||a++>2; * System.out.println(b2); * System.out.println(a); */
    		/*3 int a=5,b=10,c=5; * boolean b1=c>b&&a++>2; * System.out.println(b1); * System.out.println(a); * boolean b2=b>=a||a++>c; * System.out.println(b2); * System.out.println(a)' */
    		/*2 int a=5,b=10,c=5; * boolean b1=c>b&&a++>3; * System.out.println(b1); * System.out.println(a); * boolean b2=b>a||c++>4; * System.out.println(b2); * System.out.println(c); */
    		/*1 int a=5,b=10,c=5; * boolean b1=b<a&&c++>1; * System.out.println(b1); * System.out.println(c); * boolean b2=b>a||++c>2; * System.out.println(b2); * System.out.println(c); */

/*int a=5 a+=10;//a=a+10 System.out.println(a);//15 a*=2;//a=a*2 System.out.println(a);//30 a/=6;//a=a/6 System.out.println(a);//5 */
    		/*5 int a=5; * a+=10; * System.out.println(a); * a-=10; * System.out.println(a); * a*=6; * System.out.println(a); * a/=6; * System.out.println(a); * a%=5; * System.out.println(a); */
    		/*4 int b=6; * b+=5; * System.out.println(b);//11 * b-=6; * System.out.println(b);//5 * b*=6; * System.out.println(b);//30 * b/=5; * System.out.println(b);//6 * b%=3; * System.out.println(b);//0 */
    		/*3 int c=3; * c+=2; * System.out.println(c);//5 * c-=1; * System.out.println(c);//4 * c*=5; * System.out.println(c);//20 * c/=2; * System.out.println(c);//10 * c%=2 * System.out.println(c);//0 */
    		/*2 int d=9; * d+=1; * System.out.println(d);//10 * d-=5; * System.out.println(d);//5 * d*=10; * Sysetm.out.println(d);//50 * d/=25; * System.out.println(d);//2 * d%=5; * System.out.println(d);//2 */
    		/*1 int e=4; * e+=1; * System.out.println(e);//5 * e-=4; * System.out.println(e);//1 * e*=5; * System.out.println(e);//5 * e/=5; * System.out.println(e);//1 * e%=2; * System.out.println(e);//2 */

System.out.println(10+20+""+30);//"3030"
    		System.out.println(""+10+20+30);//"102030"
    		System.out.println(10+20+30+"");//"60"
    		int age=24;
    		System.out.println("age");//age
    		System.out.println(age);//24
    		System.out.println("age="+age);//age=24
    		System.out.println("我的年龄是"+age);
    		System.out.println("我今年"+age+"岁了");
    		String name="mgs";
    		System.out.println("大家好，我叫"+name+"我今年"+age+"岁了");
    		/*5 System.out.println(10+20+30+""); * System.out.println(10+20+""+30); * System.out.println(10+""+20+30; * int age=24; * String name="mgs"; * System.out.println(age); * System.out.println("age"); * System.out.println("age="age); * System.out.printlm("wodenianlingshi"+age); * System.out.println("wodenianlingshi"+age+"wodemingzishi"+name); */
    		/*4 System.out.println(""+10+20+30); * System.out.println(10+""+20+30); * System.out.println(10+20+""+30); * ing age=24; * String name=mgs; * System.out.println("age"); * System.out.println(age); * System.out.printlm("age="age); * System.out.println("我的年龄是"+age); * System.out.println("我的名字是"+name+"今年已经"+age+"岁了"); */
    		/*3 System.out.println(10+""+20+30); * System.out.println(10+20+""+30); * System.out.println(10+20+30+""); * int age=24; * String name ="mgs"; * System.out.println(age); * System.out.println("age"); * System.out.println("age="age); * System.out.println("my name is "+name); * System.out.println("my name is "+name+"and "+age+""old"); */
    		/*2 System.out.println(10+""+20+30); * System.out.println(10+20+''+30); * System.out.println(10+20+30+""); * int age=24; * String name="mgs"; * System.out.println("age"); * System.out.println(age); * System.out.println("age="+age); * System.out.println("我名为"+name); * System.out.println("我名为"+name+"今岁"+age); */
    		/*1 System.out.println(10+""+20+30); * System.out.println(10+20+""+30); * System.out.println(10+20+30+""); * int age=23; * String name="mgs"; * System.out.println("age"); * System.out.println(age); * System.out.println("age="age); * System.out.println("我的名字是"+name); * System.out.println("我的名字是"+name+"今年"+age+"啦"); */

int number=5;
    		int flag=number>0?1:-1;
    		System.out.println(flag);//1
    		int a=4,b=5;
    		int max=a>b?a:b;
    		System.out.println("最大值"+max);
    		/*5 int num=5; * int flag=nub>0?1:-1; * System.out.println(flag); * int a=4,b=5; * int max=a>b?a:b; * System.out.println("max="+max); */
    		/*4 int num=6; * int flag=num>5?1:0; * System.out.printlm(flag); * int a=4,b=9; * int max=a>b?a:b; * System.out.println("max is"+max); */
    		/*3 int num=2; * int flag=num>2?1:-1; * System.out.println(flag); * int a=8,b=7; * int max=a>b?a:b; * System.out.println("max="+max); */
    		/*2 int num=3; * int flag=num>1?8:6; * System.out.println(flag); * int a=4,b=5; * int max=a>b?a:b; * System.out.println("max is "+max); */
    		/*1 int num=3; * int flag=num>2?1:-1; * System.out.println(flag); * int a=6,b=7; * int min=a>b?b:a; * System.out.println("min="+min); */

int year=2020;
    		boolean flag=(year%4==0&&year%100!=0)||year%400==0;
    		String str=flag?year+"是闰年":year+"是平年";
    		System.out.println(str);
    		/*5 int year=2000; * boolean flag=(year%4==2&&year%100!=0)||year%400==0; * String str=flag?year+"是闰年":year+"是平年"； * System.out.println(str); */
    		/*4 int year=2008; * boolean flag=(year%4==0&&year%100!=0)||year%400==0; * String str=flag?year+"是闰年":year+"是平年"; * System.out.println(str); */
    		/*3 int year=2012; * boolean flag=(year%4==0&&year%100!=0)||year%400==0; * String str=flag?year+"是闰年":year+"是平年"; * System.out.println(str); */
    		/*2 int year=2013; * boolean flag=(year%4==0&&year%100!=0)||year%400==0; * String str=flag?year+"是闰年":year+"是平年"; * System.out.println(str); */
    		/*1 int year=2020; * boolean flag=(year%4==0&&year%100!=0)||year%400==0; * String str=flag?year+"是闰年":year+"是平年"; * System.out.println(str); */

[20200401155702995.png]: /images/20230528/a93515c6e014493cb417bf2d23573be8.png