Mathクラスの基本的な使い方

/*
 *  math 
 */

public class TestMath {

	public static void main(String[] args) {
		// 
        System.out.println(Math.ceil(3.2));
        System.out.println(Math.floor(3.2));
        System.out.println(Math.round(3.2));
        System.out.println(Math.round(3.8));
        //  、 、a b 
        System.out.println(Math.abs(-45));
        System.out.println(Math.sqrt(64));
        System.out.println(Math.pow(5, 2));
        System.out.println(Math.pow(2, 5));
        //Math 
        System.out.println(Math.PI);
        System.out.println(Math.E);
        // 
        System.out.println(Math.random());// [0,1)
	}

}

Randomクラスの使用

/*
 *  Randomd 
 */

public class TestRandom {
	public static void main(String[] args) {
		Random rand = new Random();
        // [0,1) double 
        System.out.println(rand.nextDouble());
        // int 
        System.out.println(rand.nextInt());
        // [0,1) float 
        System.out.println(rand.nextFloat());
        // false true
        System.out.println(rand.nextBoolean());
        // [0,10) int 
        System.out.print(rand.nextInt(10));
        // [20,30) int 
        System.out.print(20 + rand.nextInt(10));
        // [20,30) int （ ）
        System.out.print(20 + (int) (rand.nextDouble() * 10));
	}
}