JAVA编程实例1

1.Hello World编程

代码如下：

package day01;
public class HelloWorld {
	public static void main(String[] args) {
		System.out.println("HelloWorld");
	}
}

2.数据类型的演示

代码如下：

package day02;
//数据类型的演示
public class DataTypeDemo {
	public static void main(String[] args) {
		int a = 2147483647;
		a=a+1;
		System.out.println(a);
		System.out.println(5/2);
		System.out.println(5/2.0);
		System.out.println(5.0/2);
		System.out.println(2/5);
		
		long a = 10000000000L;
		long b = 1000000000L*3*10;
		long c = 1000000000*3*10L;//数据溢出
		System.out.println(a);
		System.out.println(b);
		System.out.println(c);
		double f = 3.14;
		float e =3.14F;
		double h= 3.0 , g= 2.9;
		System.out.println(h-g);

		boolean b1 = true;
		boolean b2 = false;
		//boolean只能有以上俩种，
		
		
		
		char c1 ='女';
		char c2 ='f';
		char c3 ='6';
		char c4 =' ';
		char c5 ='\\';//特殊符号用\
		char c6 ='\'';
		char c7 =65;
		int  c8 =65;
		System.out.println(c1);
		System.out.println(c2);
		System.out.println(c3);
		System.out.println(c4);
		System.out.println(c5);
		System.out.println(c6);
		System.out.println(c7);
		System.out.println(c8);
		
		
		
		int a =5;
		long b = a;
		int c = (int)b;
		long d =5;
		double e =5;
		long f=10000000000L;
		int g=(int)f;//溢出
		System.out.println(g);
		double h =3.14;
		int i =(int)h;
		System.out.println(i);//溢出
		
		
		
		
		byte b1 =5;
		byte b2 =6;
		byte b3 =(byte)(b1+b2);
		System.out.println(2+2);
		System.out.println('2'+'2');
		System.out.println('2'+2);
		System.out.println(2);
		System.out.println('2');
	
		
		int a=1,e=1;
		int b=a++;
		int c=++e;
		System.out.println(a);
		System.out.println(e);
		System.out.println(b);
		System.out.println(c);
		
	}

}

3.变量的声明与初始化

代码如下：

package day02;
public class VarDemo {
	public static void main(String[] args) {
		int a;
		int b,c,d;
		int e=250;
		int f;
		f=250;
		int q;
		int w,t,r;
		int y=250;
		int u;
	}
}

4.if条件语句

代码如下：

package day03;
public class ifDemo {
	public static void main(String[] args) {
int num =9;
		if(num%2==0){
			System.out.println(num+"为偶数");
		}
		System.out.println("over");
		double price = 700;
		if(price>500){
			price *=0.8;
		}
		System.out.println("最终金额为"+price);
	}

}

4.if…else条件语句

代码如下：

package day03;
public class ifElseDemo {
	public static void main(String[] args) {
int number =5;
		if(number%2==0){
			System.out.println(number+"是偶数");
		}else{
			System.out.println(number+"是奇数");
		}
		double price=600;
		if(price>=500){
			price *= 0.8;
		}else{
			price *= 0.9;
		}
		System.out.println("最终金额为"+price);
    }
}

5.三目运算符

1）奇偶判断与打折问题

package day03;
public class ifElseDemo {
	public static void main(String[] args) {	
		int a=10,c=10;
		int b =a++;
		int d =++c;
		System.out.println(b);
		System.out.println(d);
		short e =10;
		e +=10;
		System.out.println(e);
		System.out.println(e--);
		System.out.println(e++<++e);
		int max=a>c?a:c;
		System.out.println(max);
		System.out.println(max>10||++a>10);
		System.out.println(a);
		char o=64;
		System.out.println(o);
 }
}

2）闰年平年的判断

int year =2020;
		if(year%4== 0 && year%100!=0 ||year%400==0){
			System.out.println(year+"是闰年");
			
			
		}else{
			System.out.println(year+"是平年");
		}

3）判断最大值

int a=3,b=5,max;
		if(a>b){
			max=a;
			
		}else{
			max=b;
			
		}
		System.out.println(max);
		max=a>b?a:b;
		System.out.println(max);

6.字符串链接运算符+

int age =22;
		System.out.println("我今年"+age+"岁了");
		System.out.println("我的年龄是"+age);
		System.out.println("I am "+age+" years old");
		String name ="ch";
		System.out.println("I am "+name);
		System.out.println("my name is "+name);	

7.赋值运算符

int a=5;
		a +=10;
		System.out.println(a);
		a -=10;
		System.out.println(a);
		a *=10;
		System.out.println(a);
		a /=10;
		System.out.println(a);
		a %=10;
		System.out.println(a);
		short b=10;
		b -=10;
		System.out.println(b);

8.逻辑运算符

int a=2,b=4,c=2;
		System.out.println(a<b||a-->c);//短路问题
		System.out.println(a);
		System.out.println(a>c&&a--<c);
		System.out.println(a);
		System.out.println(a>b||a-->c);
		System.out.println(a);
		System.out.println(a<c&&a--<c);
		System.out.println(a);

9.算术运算符与关系运算符

int a=1,b=4,c=1;
		System.out.println(a==c);
		System.out.println(a!=c);
		System.out.println(a>=b);
		System.out.println(a%b==c);
		System.out.println(b/a>c);
		System.out.println(a++==c--);
		System.out.println(b%a==c);