Article directory
1. Find the most value
Define an array {33, 5, 22, 44, 55} and find the maximum value
Define an array to store 5 values
int[] arr ={
33, 5, 22, 44, 55};
Temporarily consider the data of index 0 to be the largest
int max = arr[0];
Compare each element with max
for (int i = 1; i < arr.length; i++) {
if(arr[i] > max)
{
max = arr[i];
}
But after the loop ends, max records the maximum value
System.out.println(max);
Total code block:
public class array_test {
public static void main(String[] args) {
int[] arr ={
33, 5, 22, 44, 55};
int max = arr[0];
for (int i = 1; i < arr.length; i++) {
if(arr[i] > max)
{
max = arr[i];
}
}
System.out.println(max);
}
}
Second, sum and count the number
Traversing the array and
summing Requirements: Generate 10 random numbers between -100 and store them in the array.
- Find the sum of all data
- Find the average of all data
- Count how many data are smaller than the average
(1) Define an array
int[] arr = new int[10];
(2) Generate random numbers
Random r = new Random();
(3) Store the random number in the array
for (int i = 0; i < arr.length; i++) {
int number = r.nextInt(100) + 1;
arr[i] = number;
}
- Find the sum of all data
Define the summation variable
int sum = 0;
Loop to get each element and add it to sum
for (int i = 0; i < arr.length; i++) {
sum = sum + arr[i];
}
Find the average of all data
int avg = sum / arr.length;
System.out.println("平均数是：" + avg);
Count how many data are smaller than the average
int count = 0;
for (int i = 0; i < arr.length; i++) {
if(arr[i] < avg){
count++;
}
}
System.out.println("随机数中比平均数小的有" + count + "个");
Data can be printed out for verification
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
Total code block:
import java.util.Random;
public class array_test{
public static void main(String[] args) {
int[] arr = new int[10];
Random r = new Random();
for (int i = 0; i < arr.length; i++) {
int number = r.nextInt(100) + 1;
arr[i] = number;
}
int sum = 0;
for (int i = 0; i < arr.length; i++) {
sum = sum + arr[i];
}
System.out.println("数组和是：" + sum);
int avg = sum / arr.length;
System.out.println("平均数是：" + avg);
int count = 0;
for (int i = 0; i < arr.length; i++) {
if(arr[i] < avg){
count++;
}
}
System.out.println("随机数中比平均数小的有" + count + "个");
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
}
}
3. Exchange data
Requirements: Define an array, store 1, 2, 3, 4, 5, and exchange the elements corresponding to the index as required
- Before swap: 1, 2, 3, 4, 5
- After swap: 5, 4, 3, 2, 1
(1) Define an array to store data
int[] arr ={
1, 2, 3, 4, 5};
(2) Use loop to exchange data
for(int i = 0,j = arr.length-1;i < j;i++,j--){
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
(3) Print out data
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
Total code block:
public class array_test {
public static void main(String[] args) {
int[] arr ={
1, 2, 3, 4, 5};
for(int i = 0,j = arr.length-1;i < j;i++,j--){
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
}
}
4. Shuffle the data
Requirements: Define an array, store 1-5. It is required to shuffle the order of all data in the array (random shuffle)
Define array storage 1-5
int[] arr = {
1, 2, 3, 4, 5};
Loop through the array, shuffling the order of the data starting from index 0
Random r= new Random();
for (int i = 0; i < arr.length; i++) {
int randomIndex = r.nextInt(arr.length);
int temp = arr[i];
arr[i] = arr[randomIndex];
arr[randomIndex] = temp;
}
Output the data in shuffled order
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
Total code block:
import java.util.Random;
public class array_test {
public static void main(String[] args) {
int[] arr = {
1, 2, 3, 4, 5};
Random r= new Random();
for (int i = 0; i < arr.length; i++) {
int randomIndex = r.nextInt(arr.length);
int temp = arr[i];
arr[i] = arr[randomIndex];
arr[randomIndex] = temp;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
}
}