boolean类型用于声明布尔型变量,只能是true或false中的一个
boolean lightOn = true;
一个简单的数学学习工具:
public class Main { public static void main(String args[]) { int num1 = (int)(System.currentTimeMillis() % 10); //产生随机数1 int num2 = (int)(System.currentTimeMillis() * 7 % 10); //产生随机数2 Scanner input = new Scanner((System.in)); System.out.print("What is " + num1 + " + " + num2 + "? "); int ans = input.nextInt(); System.out.println(num1 + " + " + num2 + " = " + ans + " is " + (num1 + num2 == ans)); } }
格式化控制台输出:
如果希望浮点值小数后两位,那么可以编写如下代码:
double x = 2.0 / 3; System.out.println((int)(x * 100) / 100.0);
但是使用printf更好的控制,printf的使用和C语言相似,多了布尔值的格式控制“%b”
编程练习:
1、解一元二次方程
public class Main { public static void main(String args[]) { double a, b, c, ans; Scanner input = new Scanner(System.in); System.out.print("Enter a, b, c:"); a = input.nextDouble(); b = input.nextDouble(); c = input.nextDouble(); ans = 0.0; double delta = b * b - 4 * a * c; if(delta > 0) { double x1, x2; x1 = (-1 * b + Math.pow(delta, 0.5)) / (2 * a); x2 = (-1 * b - Math.pow(delta, 0.5)) / (2 * a); System.out.println("The roots are " + x1 + " and " + x2); } else if(delta == 0) { double x; x = -1 * b / (2 * a); System.out.println("The root is " + x); } else { System.out.println("The equation has no real roots"); } } }
2、输入一个整数,判断它是不是偶数
Scanner input = new Scanner(System.in); int n = input.nextInt(); System.out.printf("Is %d an even number? %b", n, (n % 2 == 0));
java条件选择学习
时间: 2024-11-10 00:51:18