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Java、Groovy、JavaScript、Python各语言对比

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Java

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public class Client {
    public static void main(String[] args){
        System.out.println("Hello, world.");
    }
}

Groovy

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static void main(String[] args) {
    println('Hello, world.')
}

JavaScript

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console.log("Hello, world.");

Python

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if __name__ == '__main__':
    print('Hello, world.')

字符串

Java

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public class Client {
    public static void main(String[] args) {
        String a = "Hello";
        // 截取 (Hel)
        System.out.println(a.substring(0, 3));
        // 转化 (123)
        System.out.println(String.valueOf(123));
        // 拼接 (Hello, world.)
        System.out.println(a + ", world.");
        // 格式化 (Hello, I am 10.)
        System.out.println(String.format("%s, I am %d.", a, 10));
    }
}

Groovy

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static void main(String[] args) {
    def a = "Hello"
    // 截取 (Hel)
    println(a[0..3])
    // 转化 (123)
    println(String.valueOf(123));
    // 拼接 (Hello, world.)
    println(a + ", world.")
    // 格式化 (Hello, I am 10.)
    println("${a}, I am ${10}.")
}

JavaScript

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let a = "Hello";
// 截取 (Hel)
console.log(a.substr(0, 3));
// 转化 (123)
console.log(String(123));
// 拼接 (Hello, world.)
console.log(a + ", world.");
// 格式化 (Hello, I am 10.)
console.log(`${a}, I am ${10}.`);

Python

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# coding=utf-8
if __name__ == '__main__':
    a = "Hello"
    # 截取 (Hel)
    print(a[0:3])
    # 转化 (123)
    print(str(123))
    # 拼接 (Hello, world.)
    print(a + ", world.")
    # 格式化 (Hello, I am 10.)
    print("%s, I am %d." % (a, 10))
    # or
    print("{}, I am {}.".format(a, 10))

时间格式化

Java

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public class Client {
    public static void main(String[] args) {
        // 当前时间戳 (1532955845305)
        long currentTimeMillis = System.currentTimeMillis();
        System.out.println(currentTimeMillis);

        // 格式化处理 (2018-07-30 21:04:05)
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime now = LocalDateTime.now();
        String format = formatter.format(now);
        System.out.println(format);
    }
}

Groovy

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static void main(String[] args) {
    // 当前时间戳 (1532956684952)
    def currentTimeMillis = System.currentTimeMillis()
    println(currentTimeMillis)

    // 格式化处理 (2018-07-30 21:18:05)
    def formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")
    def now = LocalDateTime.now()
    def format = formatter.format(now)
    println(format)
}

JavaScript

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// 当前时间戳 (1532956509000)
let currentTimeMillis = Date.parse(new Date());
console.log(currentTimeMillis);

// 格式化处理 (2018-07-30 21:15:09)
Date.prototype.Format = function (fmt) {
    let o = {
        "M+": this.getMonth() + 1,  // 月
        "d+": this.getDate(),       // 日
        "h+": this.getHours(),      // 时
        "m+": this.getMinutes(),    // 分
        "s+": this.getSeconds(),    // 秒
        "q+": Math.floor((this.getMonth() + 3) / 3), // 季度
        "S": this.getMilliseconds() // 毫秒
    };
    if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
    for (let k in o)
        if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length === 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
    return fmt;
};
let format = new Date().Format("yyyy-MM-dd hh:mm:ss");
console.log(format);

Python

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import time
import datetime

if __name__ == '__main__':
    # 当前时间戳 (1532957083)
    print(int(round(time.time())))

    # 格式化处理 (2018-07-30 21:24:43)
    format = datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S')
    print(format)

函数

Java

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public class Client {
    public static void main(String[] args) {
        int result = plus(1, 2);
        System.out.println(result);
    }

    private static int plus(int a, int b) {
        return a + b;
    }
}

Groovy

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static void main(String[] args) {
    def result = plus 1, 2
    println(result)
}

static def plus(int a, int b) {
    // 最后一行return可省略
    return a + b
}

JavaScript

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function plus(a, b) {
    return a + b;
}

let result = plus(1, 2);
console.log(result);

Python

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def plus(a=0, b=0):
    return a + b

if __name__ == '__main__':
    result = plus(1, 2)
    print(result)

列表

Java

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public class Client {
    public static void main(String[] args) {
        // 新建
        List<String> list = new ArrayList<>();
        // 添加
        list.add("a");
        list.add("b");
        list.add("c");
        // 移除
        list.remove("c");
        // 查询
        String first = list.get(0);

        // 拼接
        List<String> added = Arrays.asList("m", "n");
        list.addAll(added);

        // 遍历
        for (String s : list) {
            System.out.println(s);
        }
    }
}

Groovy

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static void main(String[] args) {
    // 新建 & 添加
    def list = ['a', 'b']
    // 添加
    list << 'c'
    // 移除
    list -= 'c'
    // 查询
    def first = list[0]

    // 拼接
    def added = ['m', 'n']
    list += added
    // [a, b, m, n]
    println(list)

    // 遍历
    for (i in list) {
        println(i)
    }
    // or
    list.each {
        println(it)
    }
}

JavaScript

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// 新建 & 添加
let list = ['a', 'b'];
// 添加
list.push('c');
// 移除
list = list.filter(s => s !== 'c');
// 查询
let first = list[0];

// 拼接
let added = ['m', 'n'];
list = [...list, ...added];
// or
// list = list.concat(added);
// [a, b, m, n]
console.log(list);

// 遍历
for (let i = 0; i < list.length; i++) {
    console.log(list[i]);
}

Python

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# coding=utf-8

if __name__ == '__main__':
    # 新建 & 添加
    list = ['a', 'b']
    # 添加
    list.append('c')
    # 移除
    del list[2]
    # or
    # list.remove('c')
    print(list)
    # 查询
    first = list[0]

    # 拼接
    added = ['m', 'n']
    list = list + added
    # or
    # list = list.extend(added)
    # [a, b, m, n]
    print(list)

    # 遍历
    for i in list:
        print(i)

字典

Java

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public class Client {
    public static void main(String[] args) {
        // 新建
        Map<String, Integer> map = new HashMap<>();
        // 添加
        map.put("a", 1);
        map.put("b", 2);
        map.put("c", 3);
        // 移除
        map.remove("c");
        // 查询
        Integer first = map.get("a");

        // 拼接
        Map<String, Integer> added = new HashMap<>();
        added.put("m", 4);
        added.put("n", 5);
        map.putAll(added);

        // 遍历
        map.forEach((key, value) -> {
            System.out.println(key + ": " + value);
        });
    }
}

Groovy

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static void main(String[] args) {
    // 新建 & 添加
    def map = ['a': 1, 'b': 2]
    // 添加
    map['c'] = 3
    // 移除
    map.remove('c')
    // 查询
    Integer first = map.get('a')

    // 拼接
    def added = ['m': 4, 'n': 5]
    map += added

    // 遍历
    map.each {
        println(it.key + ': ' + it.value)
    }
}

JavaScript

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// 新建 & 添加
let map = {'a': 1, 'b': 2};
// 添加
map['c'] = 3;
// 移除
delete map['c'];
// 查询
let first = map['a'];

// 拼接
let added = {'m': 4, 'n': 5};
map = {...map, ...added};
console.log(map);

// 遍历
for (let key in map) {
    if (map.hasOwnProperty(key)) {
        console.log(`${key}: ${map[key]}`);
    }
}

Python

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# coding=utf-8

if __name__ == '__main__':
    # 新建 & 添加
    map = {'a': 1, 'b': 2}
    # 添加
    map['c'] = 3
    # 移除
    del map['c']
    # 查询
    first = map['a']

    # 拼接
    added = {'m': 4, 'n': 5}
    map.update(added)
    print(map)

    # 遍历
    for key, value in map.items():
        print('%s: %s' % (key, value))

文件

Java

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public class Client {
    public static void main(String[] args) throws IOException {
        File file = new File("/Users/puke/Desktop/TODO.md");
        String content = Files.readFile(file);
        System.out.println(content);
    }
}

Groovy

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static void main(String[] args) {
    def file = new File("/Users/puke/Desktop/TODO.md")
    def content = file.text
    println(content)
}

Python

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if __name__ == '__main__':
    with open("/Users/puke/Desktop/TODO.md") as f:
        content = f.read()
        print(content)

网络

Java

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public class Client {
    public static void main(String[] args) throws IOException {
        String url = "https://www.baidu.com";
        InputStream inputStream = new URL(url).openStream();
        String content = Files.readFile(inputStream);
        System.out.println(content);
    }
}

Groovy

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static void main(String[] args) {
    def url = "https://www.baidu.com"
    def content = new URL(url).openStream().text
    println(content)
}

Python

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import urllib2

if __name__ == '__main__':
    url = "https://www.baidu.com"
    response = urllib2.urlopen(url)
    content = response.read()
    print(content)

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