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java代码(尚马day01)

少_游 2022-02-09 阅读 64

(1)HelloWorld

//单行注释:类名规范:1.大写驼峰  2.见名知意 3.类名必须与java文件名一致
public class HelloWorld{
//程序的入口(函数/方法/功能)
public static void main(String[] args){
    System.out.println(100);
    System.out.println("Hello world");
}
}

//compiler编译 comment注释 font字体 author作者 descrption描述 version版本

live templates 动态模板

直接Sop即可。

(2)

/**
 * @author: sunshine
 * @description: 维护学生的基本信息
 * @data: 2022/2/9 19:38
 * @version: 0.1
 * @since: jdk11
 */
public class studentinfo {
    public static void main(String[] args){
        char gender = '男';
        String studentName = "李四";
        int studentNo = 20;
        byte age = 28;
        float score = 100;
        boolean flag = true;
        System.out.println(gender);
        System.out.println(studentName);
        System.out.println(studentNo);
        System.out.println(age);
        System.out.println(score);
        System.out.println(flag);
    }
}

//ctrl+d向下复制    ctrl+y单行删除

(3)

/**
 * @author: sunshine
 * @description:描述手机信息
 * @data: 2022/2/9  20:00
 * @version: 0.1
 * @since: jdk11
 */
public class phoneInfo {
    public static void main(String[] args){
        String brand = "小米";
        double weight = 12.4;
        int capacity = 4050;
        int price = 6999;
        double thickness = 5.3;
        System.out.println(brand);
        System.out.println(weight);
        System.out.println(capacity);
        System.out.println(price);
        System.out.println(thickness);
    }
}

(4)

/**
 * @author: sunshine
 * @description: 使用局部变量定义所有的数据类型
 * @data: 2022/2/9  20:17
 * @version: 0.1
 * @since: jdk11
 */
public class DataType {
    public static void main(String[] args){
        //整数类型
        byte by = -100;
        short sh = 100;
        int num = 1000;
        long longNum = 100L;
        //小数类型
        float f = 10.0F;
        double d = 10.1111;
        //单字符类型
        char c1 = 'a';
        char c2 = '1';
        char c3 = '我';
        char c4 = 97;//ASCII
        char c5 = '\u67d0';
        System.out.println(c1);
        System.out.println(c2);
        System.out.println(c3);
        System.out.println(c4);
        System.out.println(c5);
        //布尔类型
        boolean flag = true;
        System.out.println(flag);
        //引用类型
        String str = "hello";
        String str1 = new String("hello");//括号里是“hello”
        System.out.println(str);
        System.out.println(str1);
    }

}

(5)

/**
 * @author: sunshine
 * @description: 数据类型转换
 * @data: 2022/2/9  20:44
 * @version: 0.1
 * @since: jdk11
 */
public class DatatypeConverter {
    public static void main(String[] args){
        //自动转换
        int num = 100;
        double douNum = num;
        System.out.println(douNum);

        char ch = 'a';//97
        int num1 = ch;
        System.out.println(num1);
        //强制类型转换
        double dou = 10.45678;
        int n = (int)dou;//变量=(目标类型)原类型
        System.out.println(n);
        byte b = (byte) n;//alt+回车
        System.out.println(b);
        short s1 = 10;
        short s2 = 10;
        short num3 = (short)(s1 + s2);
        System.out.println(num3);

    }
}

(6)

/**
 * @author: sunshine
 * @description: 运算符
 * @data: 2022/2/9  20:57
 * @version: 0.1
 * @since: jdk11
 */
public class Yunsuanfu {
    public static void main(String[] args){
        //赋值运算符  算术运算符
        int num1 = 100;
        int num2 = 10;
        System.out.println(num1 + num2);//110
        System.out.println(num1 - num2);//90
        System.out.println(num1 * num2);//1000
        System.out.println(num1 / num2);//10
        System.out.println(num1 % num2);//0
        int num3 = 10;
        num3 += 10;//num3 = num3 +10;//20
        num3 -= 10;//10
        num3 /= 10;//1
        num3 *= 10;//10
        num3 %= 3;//1
        System.out.println(num3);
        //++ --
        int a = 10;
        int b = a++;//先将a的数值赋值给b,a再自增加1
        System.out.println(b);//b=10
        System.out.println(a);//a=11
        b = ++a;//a先自增加1,再将自增后的结果赋值给b
        System.out.println(b);//b=12
        System.out.println(a);//a=12
        int x = 100;
        x = ++x;//x自增加1,再赋值给,故x=101
        System.out.println(x);
        x = x++;//x直接赋值给x,故x=101.实际为:temp = x;x++;x = temp;(用到变量缓存)
        System.out.println(x);
        String name = "张三";
        int age = 30;
        System.out.println("用户名"+name);
        System.out.println("年龄"+age);

    }
}

(7)

/**
 * @author: sunshine
 * @description: 比较运算符
 * @data: 2022/2/9  21:20
 * @version: 0.1
 * @since: jdk11
 */
public class Yunsuanfu1 {
    public static void main(String[] args){
        //基本数据类型比较的是数据    占一块栈内存
        //局部变量
        int num1 = 100;
        int num2 = 200;
        System.out.println(num1 > num2);//false
        System.out.println(num1 >= num2);//false
        System.out.println(num1 < num2);//true
        System.out.println(num1 <= num2);//true
        //引用数据类型比较的是内存地址值  占据两块堆内存
        //变量和引用是一个概念,变量名称全部在队内存
        //对String而言,数据是常量,在常量池(gdk1.8之后)
        String str1 = "hello";
        String str2 = "hello";
        String str3 = new String("hello");
        System.out.println(str1);
        System.out.println(str2);
        System.out.println(str3);
        System.out.println(str1==str2);//true
        System.out.println(str1==str3);//false
        //比较用户名或者密码  比较字符串数据 字符串1.equals(字符串2)
        System.out.println(str1.equals(str3));//true
    }
}

(8)

/**
 * @author: sunshine
 * @description: 逻辑运算符
 * @data: 2022/2/9  21:39
 * @version: 0.1
 * @since: jdk11
 */
public class Yunsuanfu2 {
    public static void main(String[] args){
        //逻辑运算符:多个表达式之间运算
        //用户登录:用户名和密码一致
        String trueName = "admin";
        String truePass = "1234";
        boolean flag1 = "admin".equals(trueName);
        boolean flag2 = "123".equals(truePass);
        System.out.println(flag1 && flag2);

        int num1 = 10;
        int num2 = 100;
        //第一个表达式true 不管使用&/&& 后面的表达式都要参与运算
        System.out.println((num1 < num2) & (num1 > num2));
        System.out.println((num1 < num2) && (num1 > num2));

        //第一个表达式false,&&后面就没必要执行,而&还要执行
        //&&:短路与 推荐使用
        //&:表达式全部都要执行
        System.out.println((num1 > num2) && (num1 < num2));
        System.out.println((num1 > num2) && (num1 < num2));
        //同上
        System.out.println((num1 > num2) | (num1 < num2));
        System.out.println((num1 > num2) || (num1 < num2));
        //^异或,相同则为false
        System.out.println(false ^ true);
        //! 非,相反的结果
        System.out.println(!true);
    }
}

(9)

/**
 * @author: sunshine
 * @description: 位运算
 * @data: 2022/2/9  22:00
 * @version: 0.1
 * @since: jdk11
 */
public class Yunsuanfu3 {
    public static void main(String[] args){
        System.out.println(4 & 7);//转换成2进制进行位运算,结果为4
        //0100
        //0111
        //0100
        System.out.println(4 | 7);//7
        System.out.println(4 ^ 7);//0011,结果为3
    }

(10)

/**
 * @author: sunshine
 * @description: 三元运算符
 * @data: 2022/2/9  22:05
 * @version: 0.1
 * @since: jdk11
 */
public class Yunsuanfu4 {
    public static void main(String[] args){
        String result = (4 > 7)?"hello":"helloWorld";//helloWorld
        System.out.println(result);
        //看精度高的数据类型
        int num = (int)((5 < 1)?100:200.234);//200
        System.out.println(num);
        //求三个数的最值
        int a = 100,b = 200,c = 300;
        int max = (a > b)?a:b;
        max = (max > c)?max:c;
        //或者int max = (a > b)?((a > c)?a:c):((b > c)?b:c);
        System.out.println(max);

    }
}
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