Copy of array and array address value

A simple example of copying array address values ：1 

/*
 *  Use a simple array 
(1) Create a file called ArrayTest02 Class , stay main() Method declaration arr1 and arr2 Two variables , They are int[] An array of types .
(2) Use braces {}, hold array1 Initialize to 8 Prime number ：2,3,5,7,11,13,17,19.
(3) Show arr1 The content of .
(4) assignment arr2 The variable is equal to arr1, modify arr2 Even index elements in , Make it equal to the index value ( Such as arr[0]=0,arr[2]=2). Print out arr1.
 * 
 *  Question and answer ：arr1 and arr2 What's the relationship ？arr1 and arr2 The address values are the same , All point to the only array entity in the heap space .
 */
public class ArrayTest02 {
	public static void main(String[] args) {  
		int[] arr1,arr2;// Define two arrays 
		arr1 = new int[]{2,3,5,7,11,13,17,19};// Array one assignment 
		// Show array1 The content of 
        System.out.println(" Array before assignment arr1 Value ");
		for(int i = 0;i < arr1.length;i++){//arr1.length Get array arr1 The length of , The value is 8
			System.out.print(arr1[i] + "\t");
		}
		// assignment arr2 The variable is equal to arr1
		// Cannot be called a copy of an array .
		arr2 = arr1;// Array equivalent arr1 The address value of is assigned to the array arr2, At this time, they only want the same array in space 
		
		// modify array2 Even index elements in , Make it equal to the index value ( Such as array[0]=0,array[2]=2)
		for(int i = 0;i < arr2.length;i++){
			if(i % 2 == 0){
				arr2[i] = i;
			}	
		}
		System.out.println();
		// Print out arr1
        System.out.println(" Array after assignment arr1 Value ");
		for(int i = 0;i < arr1.length;i++){
			System.out.print(arr1[i] + "\t");
		}
	}
}

The results are shown in the figure , We found that we changed the array in the code arr2 When the value of is output arr1 But it changed , Because arr1,arr2 The same address value points to the same array in memory space, that is {2,3,5,7,11,13,17,19}, Change the array arr2 The array becomes {0,3,2,7,4,13,6,19}, Output arr1 It's also changing .

 /*2
 * Use a simple array
 * expand ： Modify the title , Realization array2 Yes array1 Copy of array
 */

/*
 *  Use a simple array 
 *  expand ： Modify the title , Realization array2 Yes array1 Copy of array 
 */
public class ArrayExer3 {
	public static void main(String[] args) {  //alt + /
		int[] array1,array2;
		
		array1 = new int[]{2,3,5,7,11,13,17,19};
		
		// Show array1 The content of 
		System.out.println(" Array before assignment arr1 Value ");
		for(int i = 0;i < array1.length;i++){
			System.out.print(array1[i] + "\t");
		}
		
		// Copy of array :
		array2 = new int[array1.length];
		for(int i = 0;i < array2.length;i++){
			array2[i] = array1[i];
		}// Each value in the two arrays corresponds to and is equal 

		
		// modify array2 Even index elements in , Make it equal to the index value ( Such as array[0]=0,array[2]=2)
		for(int i = 0;i < array2.length;i++){
			if(i % 2 == 0){
				array2[i] = i;
			}
			
		}
		System.out.println();
		// Print out array1
		System.out.println(" Array after assignment arr1 Value ");
		for(int i = 0;i < array1.length;i++){
			System.out.print(array1[i] + "\t");
		}
		System.out.println();
		System.out.println(" Array after assignment arr2 Value ");
		for(int i = 0;i < array2.length;i++){
			System.out.print(array2[i] + "\t");
		}
	}
}

At this time, the output result is equivalent to now arr1 The array is assigned to arr2, then arr2 Change the value in the array