String output formatting (Java, Python, JavaScript, Kotlin)

Preface

In daily development, string formatting is a commonly used function to help us beautify the output information.

Suppose there is such a text that needs to be formatted for output:

INFO 10000 --- [       main] AccountServiceApplication 执行时长 40 ms.

Formatting instructions

Attributes	Content description	format requirement
INFO	log level	Position 5, aligned to the left
10000	Process PID value	Position 6, displayed in the center
main	Thread name	Position 15, aligned to the right
AccountServiceApplication	Execution method name, occupancy 30, aligned to the right
40	is the execution time value	Position 6, aligned to the left

Java

The JDK comes with String.format()no centering function, so we use Apache Common-Langthe package to display it in the center.

import org.apache.commons.lang.StringUtils;

String line = "%-5s %s --- [%15s] %30s 执行时长 %-6d ms.";
System.out.println(
        String.format(line,
                "INFO",
                StringUtils.center("10000",6),
                "main",
                "AccountServiceApplication",
                40
        )
);

Reference resources: Java formatted string-Usage of String.format()

Kotlin

Since Kotlinit is Javacompatible with ., the above solution is also applicable to Kotlin.

val line = "%-5s %s --- [%15s] %30s 执行时长 %-6d ms."

println(
        line.format(
                "INFO",
                StringUtils.center("10000", 6),
                "main",
                "AccountServiceApplication",
                40
        )
)

Python

The following examples are based on Python3testing

pythonProvides powerful formatmethods for use {}as placeholders, examples:

# 若 {} 中没有添加序号（0开始）则按照参数顺序
'Hello, my name is {}, {} years old!'.format("Tinker", 45)
# Hello, my name is Tinker, 45 years old!

# 同时可以任意调整顺序
'Hello, my name is {2}, {0} years old, I come from {1}'.format(45,"China","Tinker")
# Hello, my name is Tinker, 45 years old, I come from China

# 使用参数名或者字典（需要在前面加上 ** ）
'Hello, my name is {name}, {age} years old!'.format(name="Tinker", age=45)
'Hello, my name is {name}, {age} years old!'.format(**{
   
   "name":"Tinker", "age":45})
# Hello, my name is Tinker, 45 years old!

# 填充及格式化
# :[填充字符][对齐方式 <^> 分别是靠左、居中、靠右][宽度]

# 显示身份证后四位
'ID Num: {:*>18}'.format(5437)
# ID Num: **************5437

# 显示手机号码前三位
'Phone Num: {0:*<11}'.format(188)
# Phone Num: 188********

For 前言the formatting requirements in , you can write like this:

'{level:<5} {pid:^6} --- [{thread:>15}] {method:>30} : 执行时长 {time:<6} ms'.format(level="INFO",pid=10000,thread="main",method="AccountServiceApplication",time=40)

Reference resources: python string formatting (format)

JavaScript

JavaScript and Node.js do not directly provide corresponding methods to complete the above requirements, but you can encapsulate the methods yourself.

//此代码来源自 https://github.com/component/pad/blob/master/index.js
/**
 * Pad `str` to `len` with optional `c` char,
 * favoring the left when unbalanced.
 *
 * @param {String} str
 * @param {Number} len
 * @param {String} c
 * @return {String}
 * @api public
 */
function pad(str, len, c) {
  c = c || ' ';
  str = str + "";
  if (str.length >= len) return str;
  len = len - str.length;
  var left = Array(Math.ceil(len / 2) + 1).join(c);
  var right = Array(Math.floor(len / 2) + 1).join(c);
  return left + str + right;
}

/**
 * Pad `str` left to `len` with optional `c` char.
 *
 * @param {String} str
 * @param {Number} len
 * @param {String} c
 * @return {String}
 * @api public
 */
function left(str, len, c){
  c = c || ' ';
  str = str + "";
  if (str.length >= len) return str;
  return Array(len - str.length + 1).join(c) + str;
}

/**
 * Pad `str` right to `len` with optional `c` char.
 *
 * @param {String} str
 * @param {Number} len
 * @param {String} c
 * @return {String}
 * @api public
 */
function right(str, len, c){
  c = c || ' ';
  str = str + "";
  if (str.length >= len) return str;
  return str + Array(len - str.length + 1).join(c);
}

The demand plan is as follows:

data = {
    level:"INFO",
    pid:"10000",
    thread:"main",
    method:"AccountServiceApplication",
    time:"40"
}

`${
   
   left(data.level,5)} ${pad(data.pid,6)} --- [${
   
   left(data.thread,15)}] ${
   
   left(data.method,30)} 执行时长 ${
   
   right(data.time,6)} ms.`

There are many powerful libraries in the JS camp that can meet the above needs, such as string-format