


What are the methods in Java to determine whether a string contains a specific string?
Nov 30, 2019 am 10:55 AMN ways to determine whether a string contains a certain substring:
1, startsWith()
method
2. contains()
method
3.indexOf
method
startsWith() method
There are two variants of this method that detect whether a string starts with a specified prefix.
The syntax defined by this method is as follows:
public boolean startsWith(String prefix, int toffset) or public boolean startsWith(String prefix)
Parameter description:
prefix
– The prefix to be matched.
toffset
– Where to start looking for the string.
Return value:
true and false
Related video tutorial recommendation: java learning video
Example:
import java.io.*; public class Test{ public static void main(String args[]){ String Str = new String("Welcome to Yiibai.com"); System.out.print("Return Value :" ); System.out.println(Str.startsWith("Welcome") ); System.out.print("Return Value :" ); System.out.println(Str.startsWith("Tutorials") ); System.out.print("Return Value :" ); System.out.println(Str.startsWith("Yiibai", 11) ); } }
contains method
java.lang.String.contains()
method returns true if and only if this string contains the specified sequence of char values.
Return value:
true and false
Examples are as follows:
public static void main(String[] args) { String str = "abc"; boolean status = str.contains("a"); if(status){ System.out.println("包含"); }else{ System.out.println("不包含"); } }
indexOf method
java.lang.String.indexOf()
The purpose is to find the position of a word in a string, and also to determine whether a string contains a certain character.
Return value:
int
The example is as follows:
public static void main(String[] args) { String str1 = "abcdefg"; int result1 = str1.indexOf("ab"); if(result1 != -1){ System.out.println("字符串str中包含子串“ab”"+result1); }else{ System.out.println("字符串str中不包含子串“ab”"+result1); } }
For more related tutorials, please visit: java introductory learning
The above is the detailed content of What are the methods in Java to determine whether a string contains a specific string?. 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)

Hot Topics











The core of audio and video processing lies in understanding the basic process and optimization methods. 1. The basic process includes acquisition, encoding, transmission, decoding and playback, and each link has technical difficulties; 2. Common problems such as audio and video aberration, lag delay, sound noise, blurred picture, etc. can be solved through synchronous adjustment, coding optimization, noise reduction module, parameter adjustment, etc.; 3. It is recommended to use FFmpeg, OpenCV, WebRTC, GStreamer and other tools to achieve functions; 4. In terms of performance management, we should pay attention to hardware acceleration, reasonable setting of resolution frame rates, control concurrency and memory leakage problems. Mastering these key points will help improve development efficiency and user experience.

TheTranslatorfacadeinLaravelisusedforlocalizationbyfetchingtranslatedstringsandswitchinglanguagesatruntime.Touseit,storetranslationstringsinlanguagefilesunderthelangdirectory(e.g.,en,es,fr),thenretrievethemviaLang::get()orthe__()helperfunction,suchas

The key to implementing a linked list is to define node classes and implement basic operations. ①First create the Node class, including data and references to the next node; ② Then create the LinkedList class, implementing the insertion, deletion and printing functions; ③ Append method is used to add nodes at the tail; ④ printList method is used to output the content of the linked list; ⑤ deleteWithValue method is used to delete nodes with specified values and handle different situations of the head node and the intermediate node.

Common Go image processing libraries include standard library image packages and third-party libraries, such as imaging, bimg, and imagick. 1. The image package is suitable for basic operations; 2. Imaging has a complete function and a simple API, which is suitable for most needs; 3. Bimg is based on libvips, has strong performance, which is suitable for large images or high concurrency; 4. Imagick binds ImageMagick, which is powerful but has heavy dependencies. Quickly implement image scaling and cropping. You can use the imaging library to complete it through a few lines of code in Resize and CropAnchor functions, and support multiple parameter configurations. Adding filters or adjusting tones can be achieved through the color transformation function provided by imagination, such as Graysc

In predictive analysis, SQL can complete data preparation and feature extraction. The key is to clarify the requirements and use SQL functions reasonably. Specific steps include: 1. Data preparation requires extracting historical data from multiple tables and aggregating and cleaning, such as aggregating sales volume by day and associated promotional information; 2. The feature project can use window functions to calculate time intervals or lag features, such as obtaining the user's recent purchase interval through LAG(); 3. Data segmentation is recommended to divide the training set and test set based on time, such as sorting by date with ROW_NUMBER() and marking the collection type proportionally. These methods can efficiently build the data foundation required for predictive models.

To improve the performance of Java collection framework, we can optimize from the following four points: 1. Choose the appropriate type according to the scenario, such as frequent random access to ArrayList, quick search to HashSet, and concurrentHashMap for concurrent environments; 2. Set capacity and load factors reasonably during initialization to reduce capacity expansion overhead, but avoid memory waste; 3. Use immutable sets (such as List.of()) to improve security and performance, suitable for constant or read-only data; 4. Prevent memory leaks, and use weak references or professional cache libraries to manage long-term survival sets. These details significantly affect program stability and efficiency.

Go language can be used for scientific calculations and numerical analysis, but it needs to be understood. The advantage lies in concurrency support and performance, which is suitable for parallel algorithms such as distributed solution, Monte Carlo simulation, etc.; community libraries such as gonum and mat64 provide basic numerical calculation functions; hybrid programming can be used to call C/C and Python through Cgo or interface to improve practicality. The limitation is that the ecosystem is not as mature as Python, the visualization and advanced tools are weaker, and some library documents are incomplete. It is recommended to select appropriate scenarios based on Go features and refer to source code examples to use them in depth.

Virtual threads have significant performance advantages in highly concurrency and IO-intensive scenarios, but attention should be paid to the test methods and applicable scenarios. 1. Correct tests should simulate real business, especially IO blocking scenarios, and use tools such as JMH or Gatling to compare platform threads; 2. The throughput gap is obvious, and it can be several times to ten times higher than 100,000 concurrent requests, because it is lighter and efficient in scheduling; 3. During the test, it is necessary to avoid blindly pursuing high concurrency numbers, adapting to non-blocking IO models, and paying attention to monitoring indicators such as latency and GC; 4. In actual applications, it is suitable for web backend, asynchronous task processing and a large number of concurrent IO scenarios, while CPU-intensive tasks are still suitable for platform threads or ForkJoinPool.
