Week 1: Variables and calculations & floating point calculations

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1. The first Java program

package learnJava;

public class Learn1 {
    
    

	public static void main(String[] args) {
    
    
		// TODO 自动生成的方法存根
		System.out.print("Hello World");  //Alt+/ 快捷键, Ctrl+s 保存
	}

}

2. Variables and calculations

package learnJava;

import java.util.Scanner;

public class Learn1 {
    
    

	public static void main(String[] args) {
    
    
		// TODO 自动生成的方法存根
		System.out.println("Hello World");  //Alt+/ 快捷键, Ctrl+s 保存
		Scanner in = new Scanner(System.in); 
//		System.out.println("echo:"+in.nextLine());
//		System.out.println(2+3+"=2+3="+(2+3)+"！="+2+3);  //5=2+3=5！=23
		int price = 0; // price 作为一个变量，初始化
//		final int amount = 100; //永不变
		int amount = 0;
		System.out.println("请输入票面：");
		amount = in.nextInt();
		System.out.println("请输入金额");
		price = in.nextInt();
		System.out.println(amount+"-"+price+"="+(amount-price)); //100-33=67
	}

}

3. Floating point calculation

package learnJava;

import java.util.Scanner;

public class learn_float {
    
    

	public static void main(String[] args) {
    
    
		
		int foot;
		double inch;
		Scanner in = new Scanner(System.in);
		foot = in.nextInt();
		inch = in.nextDouble();
		System.out.println("foot="+foot+",inch="+inch);
		System.out.println((foot+inch/12)*0.3048); //或者把12改成12.0
	}

}

4. The precedence of operators

5. Forced type conversion

package learnJava;

import java.util.Scanner;

public class learn_float {
    
    

	public static void main(String[] args) {
    
    	
		int foot;
		double inch;
		foot = (int)(30/3.0); //强制类型转换
		Scanner in = new Scanner(System.in);
		foot = in.nextInt();
		inch = in.nextInt();
		System.out.println("foot="+foot+",inch="+inch);
		System.out.println((int)(foot+inch/12)*0.3048*100+"cm"); 
	}

}