Programming Languages Cheat Sheet

// Slice - 动态数组，长度可变slice := []int{1, 2, 3}        // 创建并初始化 sliceslice = append(slice, 4)       // 添加元素到末尾slice[1] = 10                  // 修改索引为1的元素subset := slice[1:3]           // 切片操作，获取索引1到3的子切片（不包含3）// Array - 固定长度数组，长度不可变arr := [3]int{1, 2, 3}         // 创建长度为3的 int 数组arr[0] = 5                     // 修改元素// Map - 哈希表，键值对存储m := map[string]int{"a": 1, "b": 2}  // 创建并初始化 mapvalue, exists := m["c"]              // 通过键获取值和存在状态m["d"] = 4                           // 添加或修改键值对delete(m, "a")                       // 删除键值对// Stack 操作（使用 slice 实现）stack := []int{}               // 创建空 stackstack = append(stack, 1)       // push：入栈top := stack[len(stack)-1]    // peek：查看栈顶元素stack = stack[:len(stack)-1]  // pop：出栈// Queue 操作（使用 slice 实现）queue := []int{}              // 创建空 queuequeue = append(queue, 1)       // enqueue：入队front := queue[0]             // peek：查看队首元素queue = queue[1:]             // dequeue：出队

// Array - 数组const arr = [1, 2, 3];                 // 创建数组arr.push(4);                          // 添加元素到末尾arr[1] = 10;                          // 修改索引为1的元素const subset = arr.slice(1, 3);       // 切片：获取索引1到3的子数组（不包含3）arr.forEach(x => console.log(x));     // 遍历数组const mapped = arr.map(x => x * 2);   // 映射：对每个元素操作const filtered = arr.filter(x => x > 1); // 过滤：筛选符合条件的元素// Object - 对象const obj = {a: 1, b: 2};             // 创建对象const value = obj.c || 0;             // 获取属性，不存在时返回默认值obj.d = 4;                            // 添加或修改属性const keys = Object.keys(obj);        // 获取所有键const values = Object.values(obj);    // 获取所有值// Set - 集合，自动去重const set = new Set([1, 2, 2, 3]);    // 创建集合set.add(4);                           // 添加元素set.has(1);                           // 检查元素是否存在set.delete(1);                        // 删除元素// Map - 键值对映射const map = new Map([['a', 1], ['b', 2]]); // 创建 mapmap.set('c', 3);                       // 设置键值对map.get('a');                          // 获取值map.has('a');                          // 检查键是否存在

// List (ArrayList)List<Integer> list = new ArrayList<>();list.add(1);list.add(2);list.set(1, 10);List<Integer> subList = list.subList(0, 2);list.remove(Integer.valueOf(1));// Set (HashSet)Set<Integer> set = new HashSet<>();set.add(1);set.contains(1);set.remove(1);// Map (HashMap)Map<String, Integer> map = new HashMap<>();map.put("a", 1);map.getOrDefault("c", 0);map.containsKey("a");Set<String> keys = map.keySet();// Queue (LinkedList)Queue<Integer> queue = new LinkedList<>();queue.offer(1);Integer front = queue.poll();// Stack (Stack)Stack<Integer> stack = new Stack<>();stack.push(1);Integer top = stack.pop();Integer peek = stack.peek();

-- Table as Arrayarr = {1, 2, 3}table.insert(arr, 4)arr[2] = 10table.remove(arr, 1)-- Table as Dictionarydict = {a = 1, b = 2}dict["c"] = 3dict.d = 4value = dict.a or 0-- Common table operationscount = #arrfor i, v in ipairs(arr) do    print(i, v)endfor k, v in pairs(dict) do    print(k, v)end

// Variables - 变量声明var x int = 10                           // 完整声明var name string = "Go"isActive := true                        // 短变量声明（自动推导类型）// Operators - 运算符+, -, *, /, %                           // 算术运算符==, !=, >, <, >=, <=                   // 比较运算符&&, ||, !                               // 逻辑运算符// Functions - 函数定义func greet(name string) string {         // 参数类型和返回值类型    return fmt.Sprintf("Hello, %s", name)}

// Variables - 变量声明let x = 10;                           // 可变变量const name = "JavaScript";             // 不可变常量let isActive = true;                   // 布尔值// Operators - 运算符+, -, *, /, %                         // 算术运算符==, ===, !=, !==, >, <, >=, <=       // 比较运算符（== 值比较，=== 类型+值比较）&&, ||, !                             // 逻辑运算符in, instanceof                        // 成员检测、类型检测// Functions - 函数定义function greet(name) {    return `Hello, ${name}`;}

// Variables - 变量声明int x = 10;                      // int 类型String name = "Java";             // 字符串类型boolean isActive = true;          // 布尔类型// Operators - 运算符+, -, *, /, %                    // 算术运算符==, !=, >, <, >=, <=            // 比较运算符&&, ||, !                        // 逻辑运算符instanceof                       // 类型检测// Methods - 方法定义public String greet(String name) {    return "Hello, " + name;}

-- Variables - 变量声明globalVar = 10              -- 全局变量local localVar = 20         -- 局部变量（推荐使用）local name = "Lua"local isActive = true-- Operators - 运算符+, -, *, /, %, ^            -- 算术运算符（^ 为幂运算）==, ~=, >, <, >=, <=        -- 比较运算符（~= 为不等于）and, or, not                -- 逻辑运算符-- Functions - 函数定义function greet(name)    return "Hello, " .. name   -- .. 为字符串拼接end

// If-else if-elseif condition {} else if condition2 {} else {}// If with initializationif x := getValue(); x > 0 {    fmt.Println("positive")} else {    fmt.Println("non-positive")}// Switch statementswitch value {case 1:    fmt.Println("one")case 2:    fmt.Println("two")default:    fmt.Println("other")}

// If-else if-elseif (condition) {} else if (condition2) {} else {}// Ternary operatorresult = condition ? "yes" : "no";// Switch statementswitch (value) {    case 1:        console.log("one");        break;    case 2:        console.log("two");        break;    default:        console.log("other");}

// If-else if-elseif (condition) {} else if (condition2) {} else {}// Ternary operatorresult = condition ? "yes" : "no";// Switch statementswitch (value) {    case 1:        System.out.println("one");        break;    case 2:        System.out.println("two");        break;    default:        System.out.println("other");}// Switch expressions (Java 14+)String message = switch (value) {    case 1 -> "one";    case 2 -> "two";    default -> "other";};

-- If-elseif-elseif condition thenelseif condition2 thenelseend-- Nested conditionsif outer_condition then    if inner_condition then    else    endend-- No ternary operator in Lua-- Use if-else or logical operatorsresult = condition and "yes" or "no"

// Traditional for loopfor i := 0; i < 10; i++ {}// For range over slice/arrayfor index, item := range items {}// For range over mapfor key, value := range m {}// While loop (Go only has for)for condition {}// Infinite loopfor {}// Loop controlfor i := 0; i < 10; i++ {    if i == 5 {        break    // Exit loop    }    if i == 3 {        continue // Skip to next iteration    }}

// Traditional for loopfor (let i = 0; i < 10; i++) {}// For...of loop (iterables)for (const item of items) {}// For...in loop (object properties)for (const key in obj) {}// While loopwhile (condition) {}// Do-while loopdo {} while (condition);// Loop controlfor (let i = 0; i < 10; i++) {    if (i === 5) {        break;    // Exit loop    }    if (i === 3) {        continue; // Skip to next iteration    }}

// Traditional for loopfor (int i = 0; i < 10; i++) {}// Enhanced for loopfor (int item : items) {}// While loopwhile (condition) {}// Do-while loopdo {} while (condition);// Loop controlfor (int i = 0; i < 10; i++) {    if (i == 5) {        break;    // Exit loop    }    if (i == 3) {        continue; // Skip to next iteration    }}// Labeled loops (for nested loops)outer: for (int i = 0; i < 3; i++) {    inner: for (int j = 0; j < 3; j++) {        if (i == 1 && j == 1) {            break outer; // Exit outer loop        }    }}

-- Numeric for loopfor i = 1, 10 do          -- 1 to 10endfor i = 1, 10, 2 do       -- 1, 3, 5, 7, 9end-- Generic for loop (ipairs for arrays)for i, v in ipairs(arr) doend-- Generic for loop (pairs for dictionaries)for k, v in pairs(dict) doend-- While loopwhile condition doend-- Repeat until loop (like do-while)repeatuntil condition-- Loop controlfor i = 1, 10 do    if i == 5 then        break    -- Exit loop    end    if i == 3 then        -- No continue in Lua, use if    endend

// Multiple return values - 多返回值func divide(a, b int) (int, error) {     // 返回结果和错误    if b == 0 {        return 0, errors.New("division by zero")  // 返回错误    }    return a / b, nil                   // 返回结果，错误为 nil}// Structs - 结构体type Person struct {    Name string                          // 结构体字段    Age  int}func (p Person) Greet() string {        // 方法（值接收者）    return fmt.Sprintf("Hello, %s", p.Name)}// Goroutines - 协程go func() {                             // go 关键字启动协程    fmt.Println("goroutine")}()// Channels - 通道（协程间通信）ch := make(chan int)                    // 创建通道go func() {    ch <- 1                             // 发送数据到通道}()value := <-ch                           // 从通道接收数据

// Ternary - 三元运算符result = condition ? a : b;// Arrow Function - 箭头函数const greet = (name) => `Hello, ${name}`;// Objects - 对象定义const person = {    name: "John",    greet() {                         // 对象方法        return `Hello, ${this.name}`;    }};// Array methods - 数组方法items.forEach(item => console.log(item)); // 遍历数组const mapped = items.map(x => x * 2);     // 映射数组const filtered = items.filter(x => x > 1); // 过滤数组

// Ternary - 三元运算符result = condition ? a : b;// Classes - 类定义public class Person {    private String name;    public Person(String name) {   // 构造方法        this.name = name;    }    public String greet() {        return "Hello, " + name;    }}// Lambda - Lambda 表达式Runnable r = () -> System.out.println("Hello");Predicate<Integer> isEven = x -> x % 2 == 0;List<Integer> evens = list.stream()    .filter(isEven)                // Stream API 过滤    .collect(Collectors.toList()); // 收集为 List

local greet = function(name)    -- 匿名函数    return "Hello, " .. nameend-- Multiple return values - 多返回值function getCoordinates()    return 10, 20endlocal x, y = getCoordinates()   -- 接收多个返回值-- Tables as objects - table 作为对象使用local person = {    name = "John",    greet = function(self)        return "Hello, " .. self.name    end}person:greet()                  -- 调用方法