每日一练:双色球
红球33选6
篮球16选1
package day0701;
import java.util.Arrays;
public class Test1 {
public static void main(String[] args) {
ShuangSeQiu s = new ShuangSeQiu();
System.out.println(Arrays.toString(s.select()));
}
}
package day0701;
import java.util.Arrays;
import java.util.Random;
public class ShuangSeQiu {
int[] red = {
1,2,3,4,5,6,7,8,9,10,
11,12,13,14,15,16,17,18,19,20,
21,22,23,24,25,26,27,28,29,30,
31,32,33
};
int[] blue = {
1,2,3,4,5,6,7,8,9,10,
11,12,13,14,15,16
};
public int[] select()
{
int[] r = Arrays.copyOf(red, 33);
int[] b = Arrays.copyOf(blue, 16);
for(int i = 0;i<6;i++)
{
int j = new Random().nextInt(r.length - i)+i;
int t = r[j];
r[j] = r[i];
r[i] = t;
}
int[] result = Arrays.copyOf(r,7);
result[6] = blue[new Random().nextInt(16)];
return result;
}
}
位运算
&与
|或
^异或
~求反
>>右移位
>>>不带符号的右移位
<<左移位
00000000000000000000000001011001
00000000000000000000000000101001 &
———————————–
00000000000000000000000000001001
00000000000000000000000001011001
00000000000000000000000000101001 |
———————————–
00000000000000000000000001111001
00000000000000000000000001011001
00000000000000000000000000101001 ^
———————————–
00000000000000000000000001110000
00000000000000000000000001011001 ~
———————————–
11111111111111111111111110100110
00000000000000000000000001011001 >>2
————————————
0000000000000000000000000001011001
10000000000000000000000001011001 >>2
————————————
1110000000000000000000000001011001
10000000000000000000000001011001 >>>2
————————————
00100000000000000000000000010110
10000000000000000000000001011001 <<2
————————————
00000000000000000000000101100100
位运算
package day0702;
import java.util.Scanner;
public class Test1 {
public static void main(String[] args) {
System.out.print("输入整数:");
int n = new Scanner(System.in).nextInt();
//n = n<<24>>>24;
n = n & 0x000000FF;
System.out.println(n);
}
}
构造方法
新建对象时,执行的一个特殊方法
一个类必须有构造方法
如果不定义,编译器编译时会添加默认构造方法
public Soldier(){
System.out.println(“构造方法“);
}
创建对象只有new是创建对象,new为对象分配内存空间
构造方法不负责构造这个对象
构造方法只是构造一个对象时,执行的一个方法代码
构造方法重载
定义多个不同参数的构造方法
class A {
public A() {}
public A(int) {}
public A(int,double) {}
public A(int,double,Sring) {}
public A(String) {}
}
构造方法可以执行任何运算,完成任何功能
常见用法,用来为成员变量赋值
整数四个字节拆分合并
package day0703;
import java.util.Arrays;
import java.util.Scanner;
public class Test1 {
public static void main(String[] args) {
System.out.print("输入整数:");
int i = new Scanner(System.in).nextInt();
IntByte obj = new IntByte(i);
System.out.println(obj.getInt());
System.out.println(Arrays.toString(obj.getBytes()));
}
}
package day0703;
import java.util.Arrays;
public class IntByte {
int n;
byte[] bytes;
public IntByte() {
}
public IntByte(int n) {
this.n = n;
this.bytes = new byte[4];
int num = 24;
for (int i =0;i<this.bytes.length;i++)
{
this.bytes[i] = (byte)(n>>num);
num-=8;
}
}
public int getInt()
{
return n;
}
public byte[] getBytes()
{
return Arrays.copyOf(bytes,4);
}
}