Kasper Deng

String in Java/Python/Go/Javascript

2015-01-08
Item Java Python Go Javascript
type String str/unicode string N/A
package import String primitive primitive N/A
charset encoding determined by os ascii utf-8, unicode(rune) UCS-2
immutable Y Y Y Y 
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#!/usr/bin/env python
# -*- coding: utf-8 -*-

## Ascii Tools
>>> ord('A')
65
>>> chr(65)
'A'

Declaration & Initialization

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// Java
String demoA = null;
String demoB = "";
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# python
# Prefer using single quote for char
demoA = 'It\'s a demo A.'
# Prefer using double quote for string to align with other language
demoB = "It\'s a demo B."
chinese = "中文"   #utf-8
uchinese = u"中文" #unicode

>>> demoC = """ It's a
... demo
... C
... """
>>> demoC
" It's a \ndemo \nC\n"
>>> r"It\'s demo"
"It\\'s demo"
>>> type(demoA)
<type 'str'>
>>> del demoC
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// Go
var demoA string;
demoB := "It's a demoB"
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// Javascript
var demoStr = "demo string"
var demoStr1 = 'demo string'  // signle quote
var demoStr = "demo string"   // double quote
var demoChar = 'a'   // no char type in JS, use sigle character in string to present char
var demoPath = "\/home\/kasper"  // escape

var demoUnicode = '\u4e2d\u6587';  // unicode '中文'

ES6 - multi-line - `...`
` This is
  multi-line
  string    `

Operations

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=== encoding ===
// java
System.getProperties().getProperty("file.encoding")
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# python
sys.getdefaultencoding()
sys.setdefaultencoding("utf-8")
encode(arg1) # encode to specific encoding arg1, e.g. "utf-8", "gb2312"
decode() # -> unicode

### basic operations ###
# python
"a" + "b", "-".join(["a", "b", "c"])
"a-b-c".split("-"), "a\nb\nc".splitlines() or splitlines(True)
startwith(), endwith()
lower(), upper()
strip(), lstrip(), rstrip()
replace(), find

>>> "a" * 3
'aaa'
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// go
str1 + str2 // string concatination
len(s)        // get length of string
str1[i]       // get char from string
for i, ch := range str {
...
}
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// Javascript
str1 = '\u0041' // or double quota "\u0041"
str1 += str2;
str.length  // string length is attribute. In Java, length() is method
str.toUpperCase()
str1 === str2
str2[0] // 'H'
str2.indexOf('World')  // 6
str2.substring(0, 5);  // Hello, range not include 5
str2.substring(6);  // World

format

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// java
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# python
# support as format in C
# %[(key)][flags(-(left alignment)/+/#(i.e. #c, #X) etc)][width][.precision]typecode(d/f/s/x etc)
# %% uses for '%' escape
>>> "%(key)s=%(value)d" % dict(key = "a", value = 10)
'a=10'

# format for container objects: list, dict
{field!convertflag:formatspec: [[fill]align][sign][#][0][width][.precision][typecode]}

>>>"test {demo}".format(demo="Kasper")
'test Kasper'
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// go
// %d, %f, %s, %x, %c
fmt.Printf("The length of \"%s\" is %d \n", str, len(str))

hex(id(x)) - return obj id - memory address

本文作者：Kasper Deng
本文链接：http://kasperdeng.github.io/2015/01/08/StringInJavaPythonGoJS/
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