Found a total of 10000 related content
how to compare strings in java equals vs ==
Article Introduction：Comparing string content in Java should use equals() instead of ==. ==Compare whether the reference is the same. For example, Stringa and Stringc point to different objects, return false; equals() is used to determine whether the content is consistent, regardless of whether the object is the same; it is recommended to use "abc".equals(str) to avoid null pointers; string constant pooling makes the same literals possible to point to the same object, but cannot rely on this behavior; == can be used to determine whether it is a specific object or as a preliminary judgment for performance optimization. In short, equals() must be used to determine whether the content of the string is equal.
2025-07-22
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255
How to determine whether the pointer is valid in C language
Article Introduction：NULL is essentially a null pointer to an empty address and does not mean invalid. Relying solely on ptr == NULL to determine that the pointer is valid is not enough to capture uninitialized, released or out of boundary memory. More reliable validity checking strategies include: checking the return value after allocating memory, setting the pointer to NULL after freeing memory, checking NULL for function parameters, using assertions and developing good programming habits (initializing pointers, checking validity, setting it to NULL after freeing, be careful of pointer operation).
2025-04-03
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516
How to see if redis is started
Article Introduction：To determine whether Redis is started, you can: 1. Check whether the process exists; 2. Use redis-cli to connect to the Redis server.
2025-04-10
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699
What is the difference between == and is in Python
Article Introduction：In Python, == and is used differently. 1.== Used to compare whether the values of two objects are equal, and is suitable for most scenarios where data content consistency is required; 2.is is used to check whether two variables point to the same object in memory, mainly used for identity recognition, such as checking whether it is None. For example, two lists with the same content return True using ==, but using is to return False. Therefore, the appropriate operator should be selected according to the needs: use == to determine whether the values are the same, and use is to determine whether it is the same object.
2025-07-29
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158
solana obtains wallet token balance and optimizes it
Article Introduction：In the past few days, I have been practicing using golang to call Solana contracts and switching languages. It feels not so easy. When doing evm, some ethereum codes are implemented in go. I feel that golang is like the first language of evm.
In the morning, I read questions from group friends
need
1. Want to determine whether Solana’s address is legitimate
2. Want to determine whether the legal address holds any one of the three tokens, that is, balance > 1
I just happened to be doing some exercises, so I simply wrote them down. The ideas are as follows:
Use the wallet address and token address to calculate the token's account address, and then call GetTokenAccountBalance
lokey :=so
2024-12-26
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1178
How to check if a python string is empty or just contains spaces?
Article Introduction：There are three main ways to determine whether a Python string is empty or contains only spaces. 1. Use str.strip(): If the string is empty after the blank at both ends is removed, the original string is empty or full space; 2. Use str.isspace(): You must first confirm that the string is not empty, and then determine whether it only contains whitespace characters; 3. Combine nots and s.isspace() to uniformly determine whether the string is "invalid", that is, it is empty or contains only spaces. These methods are suitable for data cleaning, input verification and other scenarios. When selecting, it should be decided based on whether you need to distinguish between empty strings and full-space strings.
2025-06-26
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662
What is the difference between isset() and empty() in PHP?
Article Introduction：In PHP, isset() and empty() are used to check variable states, but have different uses. 1. isset() checks whether the variable is set and not null, and returns true even if the value is an empty string, 0 or false; 2. empty() checks whether the variable is empty, including empty string, 0, "0", null, false, empty array, etc., which are all considered "empty" and return true; 3. Use isset() to determine whether the variable exists, and use empty() to determine whether the variable has valid data; 4. For example, check whether the form field isset() to check whether the field is not empty; 5. Special cases such as "
2025-06-13
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771
How to Check if an Array is Empty in JavaScript
Article Introduction：The core method to determine whether an array is empty is to check whether its length attribute is 0. 1. Using arr.length===0 is the most direct and recommended way; 2. If the variable may not be an array type, you should first use Array.isArray(arr) for type checking; 3. For object arrays or nested arrays, additional traversals should be used to determine whether the element is "substantially empty" according to business logic; 4. Avoid using JSON.stringify to judge, because it is inefficient and unreliable.
2025-07-11
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900
What is the zero value of a golang struct and how does it affect behavior?
Article Introduction：In Go, the zero value of the structure means that the fields are automatically set to the default value of their respective types when they are not explicitly initialized. For example, int is 0, string is an empty string, pointer is nil, etc. Declaring an uninitialized struct variable will put it in a legal but possibly incorrect state, which will affect logical judgment, data verification and state control. 1. Determine whether the struct is zero value can be achieved by comparing it with the type zero value, but if it contains uncomparable fields, you need to use a reflection package; 2. The zero value may cause misjudgment of valid data, affect JSON serialization output, and change the struct comparison result; 3. Methods to avoid problems include using pointer fields, adding the "whether the "is set" flag, using a third-party library to determine the zero value, and encapsulation structure
2025-06-29
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808
Python check if string is valid JSON
Article Introduction：The method to determine whether a string is a legal JSON is to use json.loads() to try to parse and catch the exception. The specific steps are as follows: ① Import the json module; ② Define the function is_valid_json(s), and use the try-except structure internally to try to parse the string s; ③ If the parsing is successful, return True, otherwise capture ValueError and return False; ④ Pay attention to handling string integrity, non-empty checks and type judgments; ⑤ You can combine jsonschema for structural verification to ensure that the field exists and types are correct.
2025-07-13
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477
Should `isdigit()` Take a `char` or `int` Input?
Article Introduction：Is isdigit() Function Intended for Char or Int Input?In the provided code snippet, the if condition employs isdigit() to determine whether the...
2024-10-31
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608
