for (String s : data) { result += s; }

This code snippet iterates through a collection of String objects called "data" using a for-each loop. For each String in the collection, the value of the String is assigned to a variable called "result".

Note: Depending on the context in which this code is being used, it may not be very useful as it will only store the value of the last String in the collection.

相关问题

设计一个字符串类,实现该类的+,+=,>运算符重载

好的，以下是一个简单的字符串类的实现，其中重载了+、+=和>运算符：

#include <cstring>
#include <iostream>

class String {
public:
    // 默认构造函数
    String() : data(nullptr), len(0) {}

    // 构造函数，根据传入的字符串构造
    String(const char* s) {
        len = std::strlen(s);
        data = new char[len + 1];
        std::strcpy(data, s);
    }

    // 拷贝构造函数
    String(const String& other) {
        len = other.len;
        data = new char[len + 1];
        std::strcpy(data, other.data);
    }

    // 移动构造函数
    String(String&& other) noexcept {
        len = other.len;
        data = other.data;
        other.len = 0;
        other.data = nullptr;
    }

    // 析构函数
    ~String() {
        delete[] data;
    }

    // 重载+运算符
    String operator+(const String& other) const {
        String result;
        result.len = len + other.len;
        result.data = new char[result.len + 1];
        std::strcpy(result.data, data);
        std::strcat(result.data, other.data);
        return result;
    }

    // 重载+=运算符
    String& operator+=(const String& other) {
        len += other.len;
        char* newData = new char[len + 1];
        std::strcpy(newData, data);
        std::strcat(newData, other.data);
        delete[] data;
        data = newData;
        return *this;
    }

    // 重载>运算符
    bool operator>(const String& other) const {
        return std::strcmp(data, other.data) > 0;
    }

    // 重载赋值运算符
    String& operator=(const String& other) {
        if (this != &other) {
            delete[] data;
            len = other.len;
            data = new char[len + 1];
            std::strcpy(data, other.data);
        }
        return *this;
    }

    // 重载移动赋值运算符
    String& operator=(String&& other) noexcept {
        if (this != &other) {
            delete[] data;
            len = other.len;
            data = other.data;
            other.len = 0;
            other.data = nullptr;
        }
        return *this;
    }

    // 获取字符串长度
    size_t length() const {
        return len;
    }

    // 获取字符串数据
    const char* c_str() const {
        return data;
    }

private:
    char* data;
    size_t len;
};

// 重载输出运算符
std::ostream& operator<<(std::ostream& out, const String& s) {
    out << s.c_str();
    return out;
}

int main() {
    String s1("hello");
    String s2("world");
    String s3 = s1 + s2;
    std::cout << s3 << std::endl;
    s1 += s2;
    std::cout << s1 << std::endl;
    std::cout << (s3 > s1) << std::endl;
    return 0;
}

在上面的代码中，我们实现了一个简单的字符串类`String`，它包含了一个指向字符数组的指针`data`和一个表示字符串长度的整数`len`。在构造函数、析构函数、拷贝构造函数和移动构造函数中，我们使用了`new`和`delete`来动态分配和释放内存。在重载+和+=运算符中，我们使用了`strcat`和`strcpy`等字符串操作函数来实现字符串的拼接。在重载>运算符中，我们使用了`strcmp`函数来比较两个字符串的大小。最后，我们还重载了输出运算符`<<`，使得我们可以方便地输出一个字符串对象。

public class BERCodec { public static byte[] encodeInteger(int value) { ByteBuffer buffer = ByteBuffer.allocate(4); buffer.putInt(value); byte[] bytes = buffer.array(); int i = 0; while(i < bytes.length && bytes[i]==0){ i++; } byte[] result = new byte[bytes.length-i+2]; result[0] = 0x02; result[1] = (byte)(bytes.length-i); System.arraycopy(bytes, i, result,2 ,bytes.length-i); return result; } public static int decodeInteger(byte[] data) { int i = data[1]; byte[] s = new byte[4]; System.arraycopy(data,2,s,4-i,i); ByteBuffer wp = ByteBuffer.wrap(s); return wp.getInt(); } public static byte[] encodeOctetString(String value) { byte[] bt = value.getBytes(); byte[] bt1 = new byte[bt.length+2]; bt1[0] = 0x04; bt1[1] = (byte) bt.length; System.arraycopy(bt,0,bt1,2,bt.length); return bt1; } public static String decodeOctetString(byte[] data) { int length = decodeLength(data[1]); return new String(data, 2, length, StandardCharsets.UTF_8); } private static int decodeLength(byte lengthByte) { if ((lengthByte & 0x80) == 0) { return lengthByte; } else { int numBytes = lengthByte & 0x7F; int length = 0; for (int i = 1; i <= numBytes; i++) { length <<= 8; length |= lengthByte & 0xFF; } return length; } } }把编码和解码分开

好的，我来帮你把编码和解码分开：

编码部分：

public static byte[] encodeInteger(int value) {
    ByteBuffer buffer = ByteBuffer.allocate(4);
    buffer.putInt(value);
    byte[] bytes = buffer.array();
    int i = 0;
    while(i < bytes.length && bytes[i] == 0) {
        i++;
    }
    byte[] result = new byte[bytes.length - i + 2];
    result[0] = 0x02;
    result[1] = (byte)(bytes.length - i);
    System.arraycopy(bytes, i, result, 2, bytes.length - i);
    return result;
}

public static byte[] encodeOctetString(String value) {
    byte[] bt = value.getBytes();
    byte[] bt1 = new byte[bt.length + 2];
    bt1[0] = 0x04;
    bt1[1] = (byte) bt.length;
    System.arraycopy(bt, 0, bt1, 2, bt.length);
    return bt1;
}

解码部分：

public static int decodeInteger(byte[] data) {
    int i = data[1];
    byte[] s = new byte[4];
    System.arraycopy(data, 2, s, 4 - i, i);
    ByteBuffer wp = ByteBuffer.wrap(s);
    return wp.getInt();
}

public static String decodeOctetString(byte[] data) {
    int length = decodeLength(data[1]);
    return new String(data, 2, length, StandardCharsets.UTF_8);
}

private static int decodeLength(byte lengthByte) {
    if ((lengthByte & 0x80) == 0) {
        return lengthByte;
    } else {
        int numBytes = lengthByte & 0x7F;
        int length = 0;
        for (int i = 1; i <= numBytes; i++) {
            length <<= 8;
            length |= lengthByte & 0xFF;
        }
        return length;
    }
}