Java Array

Description

  The same type of data collection.In fact, the array is a container.We can automatically number the elements in the array from 0 to facilitate the operation of these elements.Array is a way to store data.And array can hold any type of data.

The name of the array

// type [] arrayName = new type[size]
int[] arr = new int[5];

// type [] arrayName = new type[]{element, element,...}
int[] arr = new int[]{1,2,3,4};

Initialization of the array

int[] arr = { 1, 2, 3, 4, 5 };
int[] arr2 = new int[] { 1, 2, 3, 4, 5 };

int[] arr3 = new int[3];
arr3[0] = 1;
arr3[1] = 5;
arr3[2] = 6;

Array traversal

public static void main(String[] args) {

int[] x = { 1, 2, 3 };

for (int y = 0; y < x.length; y++) {

    System.out.println(x[y]);
    
    } 
}

Array common exception

• java.lang.NullPointerException
• java.lang.ArrayIndexOutOfBoundsException

The way to sort array

1.Using arrays comes with methods

public class ArraySort{     
        public static int[] sortWithArrays( int[] args){            
            if(args == null|| args.length < 2){  
                    return args;  
            } 
            Arrays.sort(args); 
            return args; 
        }
 }

2.Bubble sorting algorithm

public class BubbleSort{     
        public static int[] sortWithBubble(int[] args){  
            if(args == null|| args.length < 2){  
                return args;  
            }
            for(int i = 0;i < args.length-1;i++){
                for (int j = i+1;j < args.length;j++){
                    if(args[j] < args[i]){
                        int temp = args[i]; 
                        args[i] = args[j];
                        args[j] = temp;
                    }
                }
            }    
            return args;
        }
 }

3.Select sorting algorithm

public class SelectSort{     
        public static int[] sortWithSelect(int[] args){
            int minIndex;
            int temp;
            if(args == null || args.length < 2){
                return;
            }
            for (int i = 0;i < args.length-1;i++){
                minIndex = i;
                for (int j = i+1;j < args.length;j++){
                    if (args[j] < args[minIndex]){
                       minIndex = j;                          
                    }          
                }
                if(minIndex != i){
                    temp = args[i];
                    args[i] = args[minIndex];
                    args[minIndex] = temp;
                }    
            }
            return args;
        }
 }

4.Insert sorting algorithm

public class InsertSort{     
        public static int[] sortWithInsert(int[] args){
            if(args == null || args.length < 2){
                return;
            }
            for (int i = 1;i < args.length;i++){
                for (int j = i;j > 0;j--){
                    if (args[j] < args[j-1]){
                        int temp = args[j];
                        args[j] = args[j-1];
                        args[j-1] = temp;
                    }      
                }                   
            }
            return args;           
        }
 }