definition

Array utility class: various methods used to manipulate arrays, such as sorting and searching
To use this method, you need to import the toolkit: import java.util.Arrays;

common method

• Binary search: arrays.binarysearch (int [] array, int value);
• The contents of the array are converted into a string for output: arrays.tostring (int [] array);
• Array sorting: arrays.sort (int [] array)
• Copy the specified array:
• Arrays.copyOf(int [] arrary, int length); Copy array by length
• System.arraycopy(Object src, int srcPos, Object dest, int destPos,int length);， Parameter information: original object, the starting position of the original object; Target array, the starting position of the target array; Copy length
• Judge whether two arrays are equal: arrays.equals (int [] array_1, int array_2);
• Fill the array with the specified elements: arrays. Fill (int [] array, int value);
• The order of array replication efficiency from high to low is: arraycopy - > copyof - > for cyclic reading

Code example

package class_1006;
import java.util.Arrays;

public class class_arrary {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		int[] num = {11,22,33,44,55,66,77,88,99,101};
		int index_t = Arrays.binarySearch(num, 99);//Binary search_ Can find
		System.out.println("The subscript in the sequence is:"+index_t);
		int index_f = Arrays.binarySearch(num, 0);//Binary search_ can't find
		System.out.println("The subscript in the sequence is:"+index_f);//The return value is - (low+1)
		
		int [] data = {101,10,88,55,66,77,33,200,109};
		System.out.println("data After array conversion:"+Arrays.toString(data));//The contents of the array are converted into string s and output directly
		String new_num = Arrays.toString(num);
		System.out.println("num After array conversion:"+new_num);//Assign value to variable before output
		
		Arrays.sort(data);//Quick sort is used
		System.out.println("num After array sorting conversion:"+Arrays.toString(data));//Output string after sorting
		
		//Copy the specified array according to the length. If the set length is greater than the length of the array, the default value of the extra array is 0
		int[] new_data = Arrays.copyOf(data, 10);
		System.out.println("data After the array is copied and replaced:"+Arrays.toString(new_data));
		
		//In this way, the length parameter controls the number of copied array elements; The starting position of the original array controls where to start the value
		//The starting position of the new array controls where to start writing
		int[] new_data_1 = new int[data.length];//Create a new array and define the length
		System.arraycopy(new_data, 2, new_data_1, 2,3);//Copies the specified array
		System.out.println("data After copying the array:"+Arrays.toString(new_data_1));
		
		boolean result = Arrays.equals(data, num);//Determine whether two arrays are equal
		System.out.println("The comparison result of the two arrays is:"+result);
		
		Arrays.fill(num, 1000);//Fills the data filled element with the specified element
		System.out.println("The result after filling is:"+Arrays.toString(num));
	}

}

//result
 The subscript in the sequence is: 8
 The subscript in the sequence is:-1
data After array conversion:[101, 10, 88, 55, 66, 77, 33, 200, 109]
num After array conversion:[11, 22, 33, 44, 55, 66, 77, 88, 99, 101]
num After array sorting conversion:[10, 33, 55, 66, 77, 88, 101, 109, 200]
data After the array is copied and replaced:[10, 33, 55, 66, 77, 88, 101, 109, 200, 0]
data After copying the array:[0, 0, 55, 66, 77, 0, 0, 0, 0]
The comparison result of the two arrays is: false
 The result after filling is:[1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000, 1000]

Two color ball case

Playing method of two-color lottery

Two color ball betting is divided into red ball number area and basketball number area. The red ball number area is 01-33 and the basketball number area is 01-16; The two-color ball has six numbers from 33 red balls in each issue, and one number from 16 blue balls is a good way to win the prize. Even if you guess the six red ball numbers and one blue ball number of the lottery number, the order is unlimited

• First prize: 6 red balls and 1 blue ball are all correct
• Second prize 6 red balls correct
• Third prize 5 red balls and 1 blue ball correct
• The fourth prize is 5 red balls correct or 4 red balls and 1 blue ball correct
• The fifth prize is 4 red balls correct or 3 red balls and 1 blue ball correct
• The sixth prize is 1 red ball, 1 blue ball, 2 red balls, 1 blue ball and 1 blue ball

analysis

• How to produce blue ball and red ball—— generation of random number
• How to receive user selected numbers?
• How to verify whether winning?
• Announce the winning numbers of this issue

Implementation steps

• Overall realization idea
  Step 1: the user selects whether it is machine selection or first choice; Machine selected random production, user input is preferred
  Step 2: receive user selected number (6 red and 1 blue)
  Step 3: system generated number (6 red and 1 blue)
  Step 4: compare the number with the user number and calculate the equivalent number
  Step 5: verify whether you win the prize
  Step 6: system number sorting
  Step 7: give the results

• Random value non repetition algorithm (system and user)

• The logic of calculating whether to win the prize

• Result output

Code example

package class_1006;

import java.util.Random;
import java.util.Scanner;
import java.util.Arrays;
public class class_two_color {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		//Preparatory work - define relevant variables
		int[] userRedBall = new int[6];//Define the red ball number selected by the user
		int userBlueBall = 0;//The blue ball number selected by the user, because there is only 1, is given a default value of 0
		int[] rebortRedBall = new int[6];//Defines the red ball number selected by the system
		int rebortBlueBall = 0;//System selected basketball number
		int redCount = 0; //The user selects the correct number of red balls
		int blueCount = 0; //The user selects the correct number of red balls
		//It is necessary to randomly generate 6 numbers that are not repeated between 1-33 (algorithm)
		//Implementation method: after the random number is generated, change the position between the random number and the last bit in the array, and the next time it is random, the array - 1
		int[] redBall = new int[33];//An array used to randomly generate red ball numbers
		for(int i=0;i<redBall.length;i++){
			redBall[i] = i+1;
		}
		//At the beginning of the game, the user needs to select the number, machine selection or manual input
		System.out.println("The two-color ball game begins. Good luck!");
		System.out.println("Please select the way to purchase the number (1: machine selection, 2: manual selection):");
		Scanner input = new Scanner(System.in);
		boolean flag = true;
		//
		while(flag){
			int isAuto = input.nextInt();//Use a variable to receive the results of the console
			//Select the number by machine or hand according to the console results
			switch (isAuto) {
				case 1:
					//Machine selection
					//redBall is an array of 1-33. userRedBall is the red ball number generated by the user. It is not repeated and corresponds to the following
					computerSelect(redBall,userRedBall);//Machine selected red ball
					Random r = new Random();
					userBlueBall = r.nextInt(16)+1;//The blue ball generated randomly in 16 bits should be + 1, because it starts from 0
					flag = false;//The loop exits, so the value of flag is changed
					break;
	
				case 2:
					//Hand selection
					System.out.println("Please select 1-33 The 6 red ball numbers between cannot be repeated");
					for(int i=0;i<userRedBall.length;i++){
						userRedBall[i] = input.nextInt();
					}
					System.out.println("Please select 1-16 1 basketball number between");
					userBlueBall = input.nextInt();
					flag = false;
					break;
				//If the value entered is not 1 or 2, go to this step
				default:
					System.out.println("Please select the way to purchase the number (1: machine selection, 2 "preferred):");
			}
		}
		//The system randomly generates red balls and puts them into the array of red balls
		computerSelect(redBall,rebortRedBall);
		//System randomly generates blue ball
		Random r = new Random();
		rebortBlueBall = r.nextInt(16)+1;
		
		//Statistical results, statistical red balls, judge several guesses
		for(int i=0;i<userRedBall.length-redCount;i++){
			for(int j=0;j<rebortRedBall.length;j++){
				//If two numbers are equal
				if(userRedBall[i]==rebortRedBall[j]){
					//Swap equal values to the last bit
					int temp = rebortRedBall[j];
					rebortRedBall[j]=rebortRedBall[rebortRedBall.length-1-redCount];
					rebortRedBall[rebortRedBall.length-1-redCount]=temp;
					redCount++;
					break;
				}		
			}
		}
		//Statistical basketball
		if(userBlueBall==rebortBlueBall){
			blueCount = 1;
		}
		//Verify whether the winner
		if(blueCount==0 && redCount<=3){
			System.out.println("Sorry, you didn't win the prize");
		}else if(blueCount==1 && redCount<3){
			System.out.println("Congratulations, you won the sixth prize, which can be exchanged for 5 yuan");
		}else if((blueCount==1 && redCount==3)||(blueCount==0 && redCount==4)){
			System.out.println("Congratulations, you won the fifth prize, which can be exchanged for 10 yuan");
		}else if((blueCount==1 && redCount==4)||( blueCount==0&&redCount==5)){
			System.out.println("Congratulations, you won the fourth prize, which can be exchanged for 200 yuan");
		}else if(blueCount==1 && redCount==5){
			System.out.println("Congratulations, you won the third prize, which can be exchanged for 3000 yuan");
		}else if(blueCount==0 && redCount==6){
			System.out.println("Congratulations, you won the second prize, which can be exchanged for 150000 yuan");
		}else if(blueCount==1 && redCount==6){
			System.out.println("Congratulations, you won the first prize, which can be exchanged for 5 million yuan");
		}else {
			System.out.println("System error, winning is invalid!");
		}
		
		//Output - publish system number
		System.out.println("The red ball number of this issue is:");
		sort(rebortRedBall);
		System.out.println(Arrays.toString(rebortRedBall));
		System.out.println("The winning basketball number of this issue is:"+rebortBlueBall);
		//Publish user number
		System.out.println("The red ball number you selected is:");
		sort(userRedBall);
		System.out.println(Arrays.toString(userRedBall));
		System.out.println("The winning basketball number of this issue is:"+userBlueBall);
		
	}
	//Bubble sorting
	public static void sort(int[] ball){
		for(int i =0;i<ball.length-1;i++){
			for(int j=0;j<ball.length-1-i;j++){
				if(ball[j]>ball[j+1]){
					ball[j]=ball[j]+ball[j+1];
					ball[j+1]=ball[j]-ball[j+1];
					ball[j]=ball[j]-ball[j+1];
				}
			}
		}
	}
	//Randomly generate multiple non repeating red balls in the specified sequence
	//ballCoubnt is a sequence of 1-33; redBall is an array placed for the generated 6 numbers
	public static void computerSelect(int [] redBall,int[] userRedball){
		Random r = new Random();
		int index = -1;//The subscript is put here because it needs to be reused
		for(int i =0;i<=userRedball.length-1;i++){
			//Randomly generate several numbers and subtract a few from the length to ensure that the selected values are not repeated
			index = r.nextInt(redBall.length-i);//The subscript of a number is randomly generated in the sequence of 1-33
			//The index subscript is the number stored in the selected value and is placed at the end of the sequence
			userRedball[i]=redBall[index];//Place the value of the subscript in the new sequence
			int temp = redBall[index];//Intermediate variable, temporarily put the stored value for exchange
			//0 should be exchanged with the last value of the sequence. When i=1, it should be exchanged with the last value of the sequence
			redBall[index]= redBall[redBall.length-1-i];
			redBall[redBall.length-1-i]=temp;			
		}
	}
}

//result
 The two-color ball game begins. Good luck!
Please select the way to purchase the number (1: machine selection, 2: manual selection):
1
 Sorry, you didn't win the prize
 The red ball number of this issue is:
[3, 10, 18, 21, 25, 32]
The winning basketball number of this issue is: 11
 The red ball number you selected is:
[3, 18, 23, 24, 26, 30]
The winning basketball number of this issue is: 16