java math和random注意项总结以及包装类

package test;

public class test8 {

    public static void main(String[] args) {
        System.out.println("计算绝对值:" + Math.abs(-1));
        System.out.println("求大于参数的最小整数:" + Math.ceil(5.6));
        System.out.println("求小于参数的最大整数:" + Math.floor(-4.2));
        System.out.println("对小数进行四舍五入的结果:" + Math.round(-4.6));
        System.out.println("求两个数的较大值:" + Math.max(2.1, -2.1));
        System.out.println("求两个数的较小值:" + Math.min(2.1, -2.1));
        System.out.println("生成大于等于0.0小于1.0的随机值:" + Math.random());
    }
}      

package test;

import java.util.Random;

public class test9 {
        public static void main(String[] args) {
            Random random1 = new Random();
            System.out.println("无参构造函数输出:");
            for (int i = 0; i < 10; i++) {
                System.out.println(random1.nextInt(100));
            }

            //
            Random random2 = new Random(21);
            System.out.println("有参构造函数输出:");
            for (int i = 0; i < 10; i++) {
                System.out.println(random2.nextInt(100));
            }


        }
    }      

package test;

import java.util.Random;

public class test10 {


    public static void main(String[] args) {
        Random random = new Random(99);
        System.out.println("产生float类型随机数:" + random.nextFloat());
        System.out.println("产生double类型随机数:" + random.nextDouble());
        System.out.println("产生int类型随机数:" + random.nextInt());
        System.out.println("产生int类型随机数:" + random.nextInt(100));

    }
}      

public class IntExam {
    public static void main(String[] args) {
        //装箱
        int num1=10;
        Integer num2=new Integer(num1);
        System.out.println(num2);

        //拆箱
        int num3=num2.intValue();
        System.out.println(num3);
    }
}      

public class IntFuncsExam {
    public static void main(String[] args) {
        System.out.println("二进制显示8:"+Integer.toBinaryString(123));
        System.out.println("十六进制显示123:"+Integer.toHexString(123));
        System.out.println("八进制显示123:"+Integer.toOctalString(123));
        System.out.println(Double.valueOf("12.99") instanceof  Double);

    }
}