A common way to sort arrays in Java is to use Arrays.sort(). For basic data type arrays, such as int[] or double[], call Arrays.sort() directly to achieve ascending sort; if you need to sort in descending order, you need to use a wrapper class (such as Integer) and pass it into the Collections.reverseOrder() comparator. String arrays are sorted in dictionary order by default, and case-insensitive sorting can be achieved through String.CASE_INSENSITIVE_ORDER. When sorting a custom object array, you need to have the class implement a Comparable interface or provide a Comparator, for example, sort according to the age field of the Person object. In addition, Arrays.sort() adopts biaxial quick sorting of basic types and TimSort for object arrays to ensure stability. It is recommended to use built-in methods directly without implementing the sorting algorithm by yourself.
Sorting arrays is a very common operation in Java. Whether it is processing numbers, strings, or custom objects, Java provides convenient methods to implement them. The easiest way is to use the Arrays.sort() method, which can quickly complete the sorting task.
Ordering of basic data type arrays
For basic data type arrays like int[] and double[] , ascending sorting can be done directly using Arrays.sort() .
for example:
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
int[] numbers = {5, 2, 9, 1, 3};
Arrays.sort(numbers);
System.out.println(Arrays.toString(numbers)); // Output [1, 2, 3, 5, 9]
}
} If you need to sort it in descending order, you can use a wrapper class (such as Integer ) and pass it in a comparator:
import java.util.Arrays;
import java.util.Collections;
public class Main {
public static void main(String[] args) {
Integer[] numbers = {5, 2, 9, 1, 3};
Arrays.sort(numbers, Collections.reverseOrder());
System.out.println(Arrays.toString(numbers)); // Output [9, 5, 3, 2, 1]
}
} Note: Basic type arrays cannot use Collections.reverseOrder() , descending order can only be achieved through manual exchange or custom sorting logic.
Sorting string arrays
String arrays are sorted in dictionary order by default, and they can also be sorted ignoring uppercase and uppercase or other methods as needed.
Example:
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
String[] names = {"banana", "Apple", "cherry", "apple"};
Arrays.sort(names);
System.out.println(Arrays.toString(names)); // Apple is ahead of apple because it is case sensitive}
}If you do not want to be case sensitive, you can pass in a case-insensitive comparator:
Arrays.sort(names, String.CASE_INSENSITIVE_ORDER);
In this way, the order of "Apple" and "apple" will not affect the overall sorting result.
Customize the sorting of arrays of objects
If you want to sort the object array of custom classes, you need to let this class implement the Comparable interface, or provide a Comparator .
For example, there is a Person class that you want to sort by age:
import java.util.Arrays;
import java.util.Comparator;
class Person {
String name;
int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return name " (" age ")";
}
}
public class Main {
public static void main(String[] args) {
Person[] people = {
new Person("Alice", 30),
new Person("Bob", 25),
new Person("Charlie", 35)
};
Arrays.sort(people, Comparator.comparingInt(p -> p.age));
System.out.println(Arrays.toString(people));
// Output from young to large by age}
}This method is very flexible, you can sort by any field, or even combine multiple conditions to sort.
Notes and tips
- For basic type arrays,
Arrays.sort()uses Dual-Pivot Quicksort, which performs well. - For object arrays, improved merge sorting (TimSort) is used to ensure stability.
- If the array is large, don’t implement the sorting algorithm yourself. Unless there are special needs, it is more efficient and safer to directly use the built-in method.
- Remember to check whether the array is empty before sorting to avoid null pointer exceptions.
Basically that's it. After mastering these methods, you should be fine when dealing with various array sorting in Java.
The above is the detailed content of how to sort an array in java. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Asynchronous Programming Techniques in Modern Java
Jul 07, 2025 am 02:24 AM
Java supports asynchronous programming including the use of CompletableFuture, responsive streams (such as ProjectReactor), and virtual threads in Java19. 1.CompletableFuture improves code readability and maintenance through chain calls, and supports task orchestration and exception handling; 2. ProjectReactor provides Mono and Flux types to implement responsive programming, with backpressure mechanism and rich operators; 3. Virtual threads reduce concurrency costs, are suitable for I/O-intensive tasks, and are lighter and easier to expand than traditional platform threads. Each method has applicable scenarios, and appropriate tools should be selected according to your needs and mixed models should be avoided to maintain simplicity
Best Practices for Using Enums in Java
Jul 07, 2025 am 02:35 AM
In Java, enums are suitable for representing fixed constant sets. Best practices include: 1. Use enum to represent fixed state or options to improve type safety and readability; 2. Add properties and methods to enums to enhance flexibility, such as defining fields, constructors, helper methods, etc.; 3. Use EnumMap and EnumSet to improve performance and type safety because they are more efficient based on arrays; 4. Avoid abuse of enums, such as dynamic values, frequent changes or complex logic scenarios, which should be replaced by other methods. Correct use of enum can improve code quality and reduce errors, but you need to pay attention to its applicable boundaries.
Understanding Java NIO and Its Advantages
Jul 08, 2025 am 02:55 AM
JavaNIO is a new IOAPI introduced by Java 1.4. 1) is aimed at buffers and channels, 2) contains Buffer, Channel and Selector core components, 3) supports non-blocking mode, and 4) handles concurrent connections more efficiently than traditional IO. Its advantages are reflected in: 1) Non-blocking IO reduces thread overhead, 2) Buffer improves data transmission efficiency, 3) Selector realizes multiplexing, and 4) Memory mapping speeds up file reading and writing. Note when using: 1) The flip/clear operation of the Buffer is easy to be confused, 2) Incomplete data needs to be processed manually without blocking, 3) Selector registration must be canceled in time, 4) NIO is not suitable for all scenarios.
How Java ClassLoaders Work Internally
Jul 06, 2025 am 02:53 AM
Java's class loading mechanism is implemented through ClassLoader, and its core workflow is divided into three stages: loading, linking and initialization. During the loading phase, ClassLoader dynamically reads the bytecode of the class and creates Class objects; links include verifying the correctness of the class, allocating memory to static variables, and parsing symbol references; initialization performs static code blocks and static variable assignments. Class loading adopts the parent delegation model, and prioritizes the parent class loader to find classes, and try Bootstrap, Extension, and ApplicationClassLoader in turn to ensure that the core class library is safe and avoids duplicate loading. Developers can customize ClassLoader, such as URLClassL
Handling Common Java Exceptions Effectively
Jul 05, 2025 am 02:35 AM
The key to Java exception handling is to distinguish between checked and unchecked exceptions and use try-catch, finally and logging reasonably. 1. Checked exceptions such as IOException need to be forced to handle, which is suitable for expected external problems; 2. Unchecked exceptions such as NullPointerException are usually caused by program logic errors and are runtime errors; 3. When catching exceptions, they should be specific and clear to avoid general capture of Exception; 4. It is recommended to use try-with-resources to automatically close resources to reduce manual cleaning of code; 5. In exception handling, detailed information should be recorded in combination with log frameworks to facilitate later
How does a HashMap work internally in Java?
Jul 15, 2025 am 03:10 AM
HashMap implements key-value pair storage through hash tables in Java, and its core lies in quickly positioning data locations. 1. First use the hashCode() method of the key to generate a hash value and convert it into an array index through bit operations; 2. Different objects may generate the same hash value, resulting in conflicts. At this time, the node is mounted in the form of a linked list. After JDK8, the linked list is too long (default length 8) and it will be converted to a red and black tree to improve efficiency; 3. When using a custom class as a key, the equals() and hashCode() methods must be rewritten; 4. HashMap dynamically expands capacity. When the number of elements exceeds the capacity and multiplies by the load factor (default 0.75), expand and rehash; 5. HashMap is not thread-safe, and Concu should be used in multithreaded
Explained: Java Polymorphism in Object-Oriented Programming
Jul 05, 2025 am 02:52 AM
Polymorphism is one of the core features of Java object-oriented programming. Its core lies in "one interface, multiple implementations". It implements a unified interface to handle the behavior of different objects through inheritance, method rewriting and upward transformation. 1. Polymorphism allows the parent class to refer to subclass objects, and the corresponding methods are called according to the actual object during runtime; 2. The implementation needs to meet the three conditions of inheritance relationship, method rewriting and upward transformation; 3. It is often used to uniformly handle different subclass objects, collection storage and framework design; 4. When used, only the methods defined by the parent class can be called. New methods added to subclasses need to be transformed downward and accessed, and pay attention to type safety.
Effective Use of Java Enums and Best Practices
Jul 07, 2025 am 02:43 AM
Java enumerations not only represent constants, but can also encapsulate behavior, carry data, and implement interfaces. 1. Enumeration is a class used to define fixed instances, such as week and state, which is safer than strings or integers; 2. It can carry data and methods, such as passing values ??through constructors and providing access methods; 3. It can use switch to handle different logics, with clear structure; 4. It can implement interfaces or abstract methods to make differentiated behaviors of different enumeration values; 5. Pay attention to avoid abuse, hard-code comparison, dependence on ordinal values, and reasonably naming and serialization.
