System.out.println("strs["+i+"]="+strs[i]);//str[0]=aa
}
//toLowerCase():
转换成小写
//toUpperCase():
转换成大写
System.out.println(str12.toLowerCase());//test.jpg
System.out.println(str12.toUpperCase());//TEST.JPG
//trim():
去前后空格
Stringstr13="abc";
System.out.println(str13.length());//5
Stringstr14=str13.trim();
System.out.println(str14);
System.out.println(str14.length());//3
//regionMatches:
测试两个字符串区域是否相等。
Stringstr15="abcdefghijk";
Stringstr16="abcdefghijk";
booleanflag=str15.regionMatches(0,str16,0,str16.length());
System.out.println("flag:
"+flag);//true
flag=str15.regionMatches(1,str16,1,str16.length()-1);
System.out.println("flag:
"+flag);//true
flag=str15.regionMatches(3,str16,3,6);//str16="defg"
System.out.println("flag:
"+flag);//true
//将“数字”组成的字符串转换为基本数据类型
inta=Integer.parseInt("1111");
System.out.println(a);
floatf=Float.parseFloat("23.45F");
System.out.println(f);
doubled=Double.parseDouble("11.22");
System.out.println(d);
//将基本数据类型转换为字符串
Strings1=String.valueOf(a);
Strings2=String.valueOf(f);
Strings3=String.valueOf(d);
/*//equals()
//==
Aa1=newA();
Aa2=newA();
System.out.println(a1.equals(a2));//false
System.out.println(a1==a2);//false*/
}
}
publicstaticvoidmain(String[]args){
//字符串与字节数组相互转化
Strings1="欢迎来abc到网星!
";
//将字符串转换成字节数组
byte[]bytes=s1.getBytes();
//将字节数组转换成字符串
Strings2=newString(bytes);
System.out.println(s2);
System.out.println("---------------------");
try{
//将字符串转换成字节数组
bytes=s1.getBytes("GBK");//ISO-8859-1UTF-8GBK
//将字节数组转换成字符串
s2=newString(bytes,"GBK");
System.out.println(s2);
System.out.println("---------------------");
bytes=s1.getBytes("UTF-8");//ISO-8859-1UTF-8GBK
s2=newString(bytes,"UTF-8");
System.out.println(s2);
System.out.println("---------------------");
bytes=s1.getBytes("ISO-8859-1");//ISO-8859-1UTF-8GBK
s2=newString(bytes,"ISO-8859-1");
System.out.println(s2);//乱码
}catch(UnsupportedEncodingExceptione){
e.printStackTrace();
}
}
}
publicstaticvoidmain(String[]args){
Strings1="你好";
Strings2=s1.concat("张三");
System.out.println(s2);
//动态修改字符串的内容
StringBuildersb1=newStringBuilder("你好");
sb1.append("张三");
System.out.println(sb1);
//获取指定位置上的字符
charch=sb1.charAt(3);//三
System.out.println(ch);
//在指定位置插入字符串
sb1.insert(2,"干啥");
System.out.println(sb1);//你好干啥张三
//字符串反转
sb1.reverse();
System.out.println(sb1);//三张啥干好你
//在指定位置删除字符串
sb1.delete(2,4);
System.out.println(sb1);//三张好你
sb1.reverse();
//在指定位置替换字符串
sb1.replace(2,4,"李四");
System.out.println(sb1);//你好李四
}
}
publicstaticvoidmain(String[]args){
Dated1=newDate();
System.out.println(d1);//d1.toString()
Dated2=newDate(1000);
System.out.println(d2);//d2.toString()
Dated3=newDate(00L);
System.out.println(d3);//d3.toString()
System.out.println(System.currentTimeMillis());//00
Dated4=newDate(35L);
System.out.println(d4);//d4.toString()
//日期格式化
SimpleDateFormatsdf=newSimpleDateFormat("yyyy年MM月dd日HH:
mm:
ss.SSSE");
//将日期类型转换为字符串
StringdateStr=sdf.format(d4);
System.out.println("dateStr:
"+dateStr);
//把(日期)字符串转换为日期类型
try{
Dated5=sdf.parse(dateStr);
System.out.println("d5:
"+d5);
}catch(ParseExceptione){
e.printStackTrace();
}
System.out.println("------------------------------------------");
//日期格式化
SimpleDateFormatsdf1=newSimpleDateFormat("yyyy年MM月dd日HH:
mm:
ss",Locale.UK);
//将日期类型转换为字符串
StringdateStr1=sdf1.format(d4);
System.out.println("dateStr1:
"+dateStr1);
publicstaticvoidmain(String[]args){
//c产生绝对值
System.out.println(m);
doubled1=Math.random();
System.out.println(d1);
//产生1到8之间的随机数
intn=(int)(Math.random()*8)+1;
System.out.println(n);
//产生1到100之间的随机数
n=(int)(Math.random()*100)+1;
System.out.println(n);
inta=Math.round(3.5643F);
System.out.println("a:
"+a);
a=Math.round(3.4643F);
System.out.println("a:
"+a);
doubled2=Math.sqrt(8);//求平方根
System.out.println("d2:
"+d2);
System.out.println("--------------------------");
//数字格式化:
普通数字、百分比、货币形式
NumberFormatnFormat=NumberFormat.getInstance();
nFormat.setMaximumFractionDigits(7);//设置小数部分的最大位数
nFormat.setMinimumIntegerDigits(3);//设置整数部分的最小位数
Strings=nFormat.format(d2);
System.out.println("8的平方根格式化后:
"+s);
System.out.println("--------------------------");
//设置语言地区
//Localelocale=Locale.getDefault();//java.util.Locale
//Localelocale=Locale.US;
//zh_CN,en_US,en_GB,zh_HK
Localelocale=newLocale("en","GB");
System.out.println(locale);
/*nFormat=NumberFormat.getCurrencyInstance();
Currencycurrency=Currency.getInstance(locale);
nFormat.setCurrency(currency);*/
nFormat=NumberFormat.getCurrencyInstance(locale);
Stringstring=nFormat.format(0.35);
System.out.println(string);//$0.35//HK$0.35//¥0.35
System.out.println("--------------------------");
Randomrandom=newRandom();//java.util.Random
n=random.nextInt(8)+1;
System.out.println("n="+n);
/正则表达式
publicclassRegexDemo{
publicstaticvoidmain(String[]args){
、
Stringregex="\\dhello";
booleanflag=s1.matches(regex);
Stringresult=flag?
"匹配成功":
"匹配失败";
System.out.println(result);
System.out.println("-----------------------");
s1="029-";
regex="[0]\\d{2,3}-[2-8]\\d{6,7}";
flag=s1.matches(regex);
result=flag?
"匹配成功":
"匹配失败";
System.out.println(result);
}
}