黑马程序员-JAVA-字符串与正则表达式粗解

Java中的字符串处理

String 类型

String的常用方法演示

//source
String source="今天，IDE这个词和一些没有关连性的命令列工具（像vi"
+ "、emacs、make）是一种对照，虽然你可以把Unix当成是一个IDE，"
+ "但是多数的程序开发人员会把IDE当成是一个可以完成各种开发工作的一个程序，"
+ "这个IDE程序提供许多的功能，例如：制作、修改、编译、发布、调试。";
sp(source);

//if?
sp("startWith a ?:"+source.startsWith("a"));
sp("endsWith 。 ?:"+source.endsWith("。"));
sp("contains Unix ?:"+source.contains("Unix"));
sp("isEmpty ?:"+source.isEmpty());

//+ operator
sp(source+43243+false+932754295L+null+46468.74643+864.2f);//Primitive
sp(source+"clause"+new Object()+Void.class);//reference

//modify
sp(source.toLowerCase());
sp(source.toUpperCase());
sp(source.trim().replace('一', '二'));

//transform
sp(source.toCharArray());

StringBuffer

StringBuilder

StringBuffer 和StringBuilder的演示

private static void testStringBuffer() {
final int count=10000;
prepareALOT(count);
//append test
StringBuffer sb=new StringBuffer();
long start,end;
start=System.nanoTime();
for (int i = 0; i < ALOT.length; i++) {
sb.append(ALOT[i]);
}
end=System.nanoTime();
sp("StringBuffer append cost:"+(end-start));

//edit test
List<String> sf = Arrays.asList(Arrays.copyOf(ALOT, ALOT.length));
Collections.shuffle(sf);
sb.reverse();
start=System.nanoTime();
for (int i = 0; i < count; i++) {
sb.delete(i, i+5);
sb.insert(i, sf.get(i));
}
end=System.nanoTime();
sp("StringBuffer edit cost:"+(end-start));
}

private static void testStringBuilder() {
final int count=10000;
prepareALOT(count);
//append test
StringBuilder sb=new StringBuilder();
long start,end;
start=System.nanoTime();
for (int i = 0; i < ALOT.length; i++) {
sb.append(ALOT[i]);
}
end=System.nanoTime();
sp("StringBuilder append cost:"+(end-start));

//edit test
List<String> sf = Arrays.asList(Arrays.copyOf(ALOT, ALOT.length));
Collections.shuffle(sf);
sb.reverse();
start=System.nanoTime();
for (int i = 0; i < count; i++) {
sb.delete(i, i+5);
sb.insert(i, sf.get(i));
}
end=System.nanoTime();
sp("StringBuilder edit cost:"+(end-start));
}

private static void prepareALOT(int count) {
if(ALOT==null){
ALOT=new String[count];
}else if(ALOT.length!=count){
ALOT=new String[count];
}else{
return;
}
Random r=new Random();
for (int i = 0; i < ALOT.length; i++) {
char[] c=new char[8];
for (int i2 = 0; i2 < c.length; i2++) {
int rp = r.nextInt(52);
if(rp>26){
c[i2]=(char)(rp+'a'-26);
}else{
c[i2]=(char)(rp+'A');
}
}
ALOT[i]=new String(c);
}
}

private static String[] ALOT;

StringBuffer append cost:1588992
StringBuffer edit cost:217009831
StringBuilder append cost:913430
StringBuilder edit cost:169428186

正则表达式

正则表达式简介

Java中的正则表达式

'\'

([{\^-$|}])?*+.

\

\

\\

[]

|

-

&&

a-x&&[^b]

.

\d

\D

\s

\S

\w

\W

^

$

\b

\B

\A

\G

\Z

\z

Pattern类

(?i)

(?x)

(?m)

(?s)

(?u)

(?d)

PatternSyntaxException异常

Matcher类

简单的Java正则表达式演示

//match string
Pattern p=Pattern.compile("insr");
sp(p.matcher("insr").matches());

//match with simple class
p=Pattern.compile("[iard]nsr");
sp(p.matcher("insr").matches());

//match with more classes
p=Pattern.compile("[a-z&&[^r-x]][\\w]{2}r\\d");
sp(p.matcher("insr3").matches());

//matches multiple
p=Pattern.compile("[1258]\\d{4}(\\d)\\1{4}");
sp(p.matcher("1384522222").matches());

//match group
p=Pattern.compile("(\\w{2,20})://(((www|\\w+)\\.)+(\\w{1,20})\\.([a-z]{2,3}))((/[\\w]+)*)(.*)(#[\\w]+)?(\\?[\\w]+)?");
Matcher m=p.matcher("http://hllvm.group.iteye.com/group/topic/45665#ejotj?teo=52646");
sp(m.matches());
for (int i = 0; i < m.groupCount()+1; i++) {
sp(m.group(i));
}