Python、Operator、String、Java：程序中常用的运算符和字符串操作

Python 笔记

运算符和字符串操作在程序设计中非常常用。本篇文章将会从多个方面阐述这一主题。

一、运算符

运算符是一种用来执行特定数学或逻辑运算的符号。Python中的运算符包括：算数运算符、比较运算符、赋值运算符、逻辑运算符、位运算符等多种类型。

算数运算符是最基本的运算符之一，它们用于执行基本的算术操作，如加、减、乘、除等。

a = 10
b = 3
print("a + b =", a + b)   # 输出a + b = 13
print("a - b =", a - b)   # 输出a - b = 7
print("a * b =", a * b)   # 输出a * b = 30
print("a / b =", a / b)   # 输出a / b = 3.3333333333333335
print("a // b =", a // b) # 输出a // b = 3
print("a % b =", a % b)   # 输出a % b = 1
print("a ** b =", a ** b) # 输出a ** b = 1000

比较运算符用于比较两个变量的值，并返回一个布尔值（True或False）。

a = 10
b = 5
print("a > b =", a > b)   # 输出a > b = True
print("a < b =", a < b)   # 输出a < b = False
print("a == b =", a == b) # 输出a == b = False
print("a != b =", a != b) # 输出a != b = True
print("a >= b =", a >= b) # 输出a >= b = True
print("a <= b =", a <= b) # 输出a <= b = False

赋值运算符用于将右边的值赋给左边的变量。

a = 10
b = 5
c = a + b
print("c =", c)          # 输出c = 15
a += b
print("a += b：a =", a)  # 输出a += b：a = 15
a -= b
print("a -= b：a =", a)  # 输出a -= b：a = 10
a *= b
print("a *= b：a =", a)  # 输出a *= b：a = 50
a /= b
print("a /= b：a =", a)  # 输出a /= b：a = 10.0
a %= b
print("a %= b：a =", a)  # 输出a %= b：a = 0.0
a **= b
print("a **= b：a =", a) # 输出a **= b：a = 0.0

逻辑运算符用于组合多个条件，并返回一个布尔值。

a = 10
b = 5
c = 3
print("a > b and b > c =", a > b and b > c) # 输出a > b and b > c = True
print("a > b or b < c =", a > b or b < c)   # 输出a > b or b < c = True
print("not a > b =", not a > b)              # 输出not a > b = False

位运算符是用来执行位运算的运算符。

a = 10
b = 5
print("a & b =", a & b)     # 输出a & b = 0
print("a | b =", a | b)     # 输出a | b = 15
print("a ^ b =", a ^ b)     # 输出a ^ b = 15
print("~a =", ~a)           # 输出~a = -11
print("a << 2 =", a << 2)   # 输出a << 2 = 40
print("a >> 2 =", a >> 2)   # 输出a >> 2 = 2

二、字符串操作

字符串是程序中常用的数据类型之一。在Python中，字符串可以使用单引号、双引号或三引号来表示。字符串操作是对字符串进行操作的一些方法，包括格式化、拆分、连接、替换、大小写转换等。

字符串格式化是指将变量的值插入到占位符中，以便动态生成字符串。

name = "Tom"
age = 18
print("My name is %s, I am %s years old." % (name, age)) # 输出My name is Tom, I am 18 years old.

字符串拆分是指将字符串按照指定的分隔符进行拆分。

string = "a,b,c,d,e"
list = string.split(",")
print(list) # 输出['a', 'b', 'c', 'd', 'e']

字符串连接是指将多个字符串拼接成一个字符串。

string1 = "hello"
string2 = "world"
string = string1 + " " + string2
print(string) # 输出hello world

字符串替换是指将字符串中的某些字符替换成其他字符。

string = "hello world"
new_string = string.replace("world", "Python")
print(new_string) # 输出hello Python

字符串大小写转换是指将字符串中的字母大小写进行转换。

string = "Hello World"
lower_string = string.lower()
upper_string = string.upper()
print(lower_string) # 输出hello world
print(upper_string) # 输出HELLO WORLD

三、Java程序中常用的运算符和字符串操作

Java语言是一种广泛使用的面向对象编程语言，同样也包含了多种运算符和字符串操作。

Java中的运算符和Python中的运算符类似，包括算数运算符、比较运算符、赋值运算符、逻辑运算符、位运算符等多种类型。

Java中的字符串操作与Python中的字符串操作也非常相似，包括字符串格式化、拆分、连接、替换、大小写转换等。

public class Main {
  public static void main(String[] args) {
    // 算数运算符
    int a = 10;
    int b = 3;
    System.out.println("a + b = " + (a + b));   // 输出a + b = 13
    System.out.println("a - b = " + (a - b));   // 输出a - b = 7
    System.out.println("a * b = " + (a * b));   // 输出a * b = 30
    System.out.println("a / b = " + (a / b));   // 输出a / b = 3
    System.out.println("a % b = " + (a % b));   // 输出a % b = 1
    System.out.println("a += b：a = " + (a += b)); // 输出a += b：a = 13
    System.out.println("a -= b：a = " + (a -= b)); // 输出a -= b：a = 10
    System.out.println("a *= b：a = " + (a *= b)); // 输出a *= b：a = 30
    System.out.println("a /= b：a = " + (a /= b)); // 输出a /= b：a = 10
    System.out.println("a %= b：a = " + (a %= b)); // 输出a %= b：a = 1

    // 比较运算符
    int c = 5;
    System.out.println("a > b = " + (a > b));   // 输出a > b = true
    System.out.println("a < b = " + (a < b));   // 输出a < b = false
    System.out.println("a == b = " + (a == b)); // 输出a == b = false
    System.out.println("a != b = " + (a != b)); // 输出a != b = true
    System.out.println("a >= b = " + (a >= b)); // 输出a >= b = true
    System.out.println("a <= b = " + (a <= b)); // 输出a <= b = false

    // 逻辑运算符
    System.out.println("a > b && b > c =" + (a > b && b > c)); // 输出a > b && b > c = true
    System.out.println("a > b || b < c =" + (a > b || b < c));   // 输出a > b || b < c = true
    System.out.println("!(a > b) =" + !(a > b));                // 输出!(a > b) = false

    // 位运算符
    int d = 5;
    System.out.println("a & b = " + (a & b));     // 输出a & b = 1
    System.out.println("a | b = " + (a | b));     // 输出a | b = 15
    System.out.println("a ^ b = " + (a ^ b));     // 输出a ^ b = 14
    System.out.println("~a = " + (~a));           // 输出~a = -31
    System.out.println("a << 2 = " + (a << 2));   // 输出a << 2 = 40
    System.out.println("a >> 2 = " + (a >> 2));   // 输出a >> 2 = 2

    // 字符串格式化
    String name = "Tom";
    int age = 18;
    System.out.printf("My name is %s, I am %d years old.", name, age); // 输出My name is Tom, I am 18 years old.

    // 字符串拆分
    String str = "a,b,c,d,e";
    String[] array = str.split(",");
    System.out.println(Arrays.toString(array)); // 输出[a, b, c, d, e]

    // 字符串连接
    String str1 = "hello";
    String str2 = "world";
    String string = str1 + " " + str2;
    System.out.println(string); // 输出hello world

    // 字符串替换
    String oldString = "hello world";
    String newString = oldString.replace("world", "Java");
    System.out.println(newString); // 输出hello Java

    // 字符串大小写转换
    String s = "Hello World";
    String lowStr = s.toLowerCase();
    String upStr = s.toUpperCase();
    System.out.println(lowStr); // 输出hello world
    System.out.println(upStr);  // 输出HELLO WORLD
  }
}