Error: sorting and subscript out of bounds

Error message ：
java.lang.ArrayIndexOutOfBoundsException: Index 8 out of bounds for length 8
java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 8
-1,8 Index exceeds array index ( If you use i–,j– It's possible -1 The corner marker is out of bounds )

The code is as follows ：

public class StringTest_1
{
    
	public static void main(String[] args)
	{
    
		String[] arr={
    "abc","NBA","CBA","java","Hong","demo","qq","WX"};
		printArray(arr);     
		sortString(arr);
		printArray(arr);
		maopaoString(arr);
		printArray(arr);
	}
	// Bubble sort 
	public static void maopaoString(String[] arr)
	{
    		
		for(int i=0;i<arr.length-1;i++)
			for(int j=0;j<arr.length-1-i;j++)
			{
    
				if(arr[j].compareTo(arr[j+1])>0)
					swap(arr,j,j+1);     //swap(arr,arr[j],arr[j+1]); 
			}
	}
	// Selection sort 
	public static void sortString(String[] arr)
	{
    
		for(int i=0;i<arr.length-1;i++)    
			for(int j=i+1;j<arr.length;j++)
			{
    
				if(arr[i].compareTo(arr[j])>0)
					swap(arr,i,j);//swap(arr,arr[i],arr[j]); 
			}
	}
	// Exchange elements 
	public static void swap(String[] arr,int i,int j)
	{
    
		String temp=arr[i];
		arr[i]=arr[j];
		arr[j]=temp;
	}
	 Traverse and print the array 
	public static void printArray(String[] arr)
	{
    
		System.out.print("[");
		for(int i=0;i<arr.length;i++)
		{
    
			if(i!=arr.length-1)
				System.out.print(arr[i]+",");
			else
				System.out.println(arr[i]+"]");
		}
	}
}

	// Selection sort ： Take out one element at a time according to the index order and compare it with each subsequent element one by one 
	public static void sortString(String[] arr)
	{
    
		for(int i=0;i<arr.length-1;i++)    
			for(int j=i+1;j<arr.length;j++)
			{
    
				if(arr[i].compareTo(arr[j])>0)
					swap(arr,i,j);//swap(arr,arr[i],arr[j]); 
			}
	}

   Outer loop ：i To arr.length-1, common arr.length-2 Secondary ranking , That is the 0 Take out each of the penultimate elements once , And compared with the following elements, of course, here is the matter of inner loop , Because there is no element after the last element , So it is 0<arr.lengrh-1.arr[i] It's the elements taken out by the outer loop every time .
   Inner loop ：j To arr.length, Each element you take out should be compared with its subsequent elements , therefore j=i+1, Every time the external circulation is added , The number of internal loop comparisons is one less , By analogy , So the elements from the outer loop will be compared with the last one every time , Until the penultimate element is compared with the last element , To complete the order .
Be careful that the corner marker is out of bounds , If I take arr[i] It's the last element , Also with arr[j] The comparison will cross the line

	// Bubble sort ： The position of one element per trip , Adjacent index comparison 
public static void maopaoString(String[] arr)
{
    		
	for(int i=0;i<arr.length-1;i++)
		for(int j=0;j<arr.length-1-i;j++)
		{
    
			if(arr[j].compareTo(arr[j+1])>0)
				swap(arr,j,j+1);     //swap(arr,arr[j],arr[j+1]); 
		}
}

   Outer loop ： Total number of external circulation control trips , One element per trip , By analogy , When the last element is left in the row , There are no elements to compare with , So is arr.length-1 Lying order

   Inner loop ： The inner loop controls the sequencing of each trip ,arr[j] And arr[j+1] Compare , Every two adjacent elements should be compared , The first row is the largest ( Or the smallest ) The element of will be placed in the last Location arr.length, By analogy , The first element of the last trip arr[0] With the second element arr[1] Compare , So the number of comparisons per trip is arr.length-1-i Time .

Be careful that the corner marker is out of bounds , If I take arr[j] It's the last element , Also with arr[j+1] The comparison will cross the line