JAVA's basic knowledge[2]2009-01-12-From

the default value:

int 0

float 0.0

boolean false

引用型 null

private 私有 自己拥有访问权限

public 共有 自由访问

无 友好 同包内可访问

final class can't be extended.

abstract class can't be created.

if a class which is a son of some class,it must define all of abstract method of its father's class.

if a class has abstract method,it must be a abstract class.

interface body includes constant define and method define withour achieved.

initialize array: int x[]={1,2,3,4,5}

String: it is a class.

Initial method: String()

String([constant String])

String([String])

String(char a[])

String(char a[],startIndex,endIndex)

String(byte[])

String(byte[],startIndex,length)

common method: [String].length()

[String].startsWith()

[String].endsWith()

[String].equals()

[String].toUpperCase()

[String].toLowerCase()

[String].concat([String])//connect two strings

[String].toCharArray()

[String].charAt(index)

to inteager Inteager.parseInt([String])

to long Long.parseLong([String])

to float Float.valueOf([String]).floatValue()

to double Double.valueOf([String]).doubleValue()

to byte[] [String].getBytes()

number to string String.valueOf([number])

search [String].indexOf([String])

[String].indexOf([String],startIndex)

substring [String].substring(startIndex)

[String].substring(startIndex,endIndex)

replace [String].replace(oldChar,newChar)

trim space [String].trim()

analyse string StringTokenizer([String])//is a class.

StringTokenizer([String],delimString)

[StringTokenizer].nextToken()//get next word

[StringTokenizer].hasMoreTokens()

[StringTokenizer].countTokens()

get current time

Date date=new Date();

long time=System.currentTimeMillis();//millisecond counted from Jan 1,0:0,1970

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snigoal@Wang,HUST.Wuhan.China