Java about arrays, rabbitmqpdf Baidu cloud

java arrays rabbitmqpdf baidu cloud

Arrays.sort(arr); // Sort the array in ascending order

for(int i=0;i<arr.length;i++) { // The output array

System.out.print(arr[i]+" ");

}

}

}

Output:0 1 2 3 4 5 6 7 8 9

2. Arrays.sort(T[] a, int fromIndex, int toIndex) Sort the array in ascending order within the specified range

import java.util.Ar

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rays; // Import Java.util.Arrays class

public class Taxis {

public static void main(String[]args) {

int arr[]=new int[] {2,3,7,6,4,9,0,1,8,5}; // Declaration array

Arrays.sort(arr,arr.length/2,arr.length); // Sort the second half of the array

for(int i=0;i<arr.length;i++) { // The output array

System.out.print(arr[i]+" ");

}

}

}

Output:2 3 7 6 4 0 1 5 8 9

3. Arrays.sort(T[] a, Comparator<? super T> c) Sorts the specified array of objects according to the order raised by the specified comparator .

null

Use sort() The default method is to sort in ascending order , What should we do if we want to sort in descending order ? At this time, we need to realize Comparator Interface to customize the comparison method .

import java.util.Arrays;

import java.util.Comparator;

public static void main(String[]args) {

Integer arr[]=new Integer[] {2,3,7,6,4,9,0,1,8,5};

// By anonymous inner class Comparator Interface

Arrays.sort(arr, new Comparator() {

@Override

// This method is used to compare the size of two numbers , Sort the positive and negative of the returned results , If we use arr2 - arr1 Sort in descending order

public int compare(Integer arr1, Integer arr2) {

return arr2 - arr1;

}

});

for(int i=0;i<arr.length;i++) {

System.out.print(arr[i]+" ");

}

}

Output: 9 8 7 6 5 4 3 2 1 0

Because we can customize the comparator , So the data we compare is not limited to the basic data types , For arrays 、 The same applies to all classes .

Compare the first number of two-dimensional arrays

import java.util.Arrays;

import java.util.Comparator;

public class Taxis {

public static void main(String[]args) {

int [][]arrs=new int[][] { // Create a 2D array

{2,3,7},

{6,4,9},

{1,8,5}

};

Arrays.sort(arrs, new Comparator<int[]>() { // Define comparison method : Compare the first number of each row of the array

public int compare(int[] arrs1, int[] arrs2) {

return arrs1[0] - arrs2[0];

}

});

for(int i=0;i<arrs.length;i++) { // Output results

for(int j=0;j<arrs[0].length;j++) {

System.out.print(arrs[i][j]+" ");

}

System.out.println();

}

}

}

Output:

1 8 5

2 3 7

6 4 9

Compare classes in a certain way :

import java.util.Arrays;

import java.util.Comparator;

class Circle{ // Customize Circle class

double r;

public Circle(double r) {

this.r=r;

}

public double area() {

return 3.14rr;

}

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