stringbuffer截取字符串的下标(解析springmvc工作流程)
java中表示字符串的有三个类:string、stringbuffer和stringbuilder。其中,string的长度是不可变的,而stringbuffer和stringbuilder是长度可变的。对于stringbuffer和stringbuilder来说,两者的api几乎一模一样,因为两者有共同的父类:abstractstringbuilder。区别在于stringbuffer的大部分方法都是被synchronized关键字修饰,是线程安全的,而stringbuilder则与其相反。
所以本篇就对stringbuffer和stringbuilder类比着来进行介绍。
- 构造器
stringbuffer和stringbuilder的构造器都有三个,分别如下:
stringbuffer的构造器:
- new stringbuffer(int capacity)
- new stringbuffer(string str)
- new stringbuffer(charsequence seq)
stringbuilder的构造器:
- new stringbuilder(int capacity)
- new stringbuilder(string str)
- new stringbuilder(charsequence seq)
对比两者构造器发现,它们对构造器的重载都施行了同样的方式,可以传入一个整数的容量,可以传一个字符串值,甚至可以传一个字符序列的对象。对于java来说,常用的字符序列对象就是我们认知中的string, stringbuffer和stringbuilder。关于stringbuilder和stringbuffer的使用的示例代码如下所示:
public class stringtest {
public static void main(string[] args) throws ioexception {
// 初始化一个容量为16,但没有值的空stringbuffer对象
stringbuffer strbuffer = new stringbuffer(16);
system.out.println("strbuffer:" + strbuffer + ", 容量为:" + strbuffer.capacity() + ", 长度为:"
+ strbuffer.length());
// 初始化一个容量为16,但没有值的空stringbuilder对象
stringbuilder strbuilder = new stringbuilder(16);
system.out.println("strbuilder:" + strbuilder + ", 容量为:" + strbuilder.capacity() + ", 长度为:"
+ strbuilder.length());
// 根据一个字符串初始化一个stringbuffer对象
stringbuffer strbuffer2 = new stringbuffer("how are you");
system.out.println("strbuffer2的值为:" + strbuffer2 + ", 容量为:" + strbuffer2.capacity() + ", 长度为:"
+ strbuffer2.length());
// 根据一个字符串初始化一个stringbuilder对象
stringbuilder strbuilder2 = new stringbuilder("how old are you");
system.out.println("strbuilder2的值为:" + strbuilder2 + ", 容量为:" + strbuilder2.capacity() + ", 长度为:"
+ strbuilder2.length());
// 根据一个字符序列对象如stringbuilder来初始化一个stringbuffer对象
stringbuilder strbuffer3 = new stringbuilder(strbuilder);
system.out.println("strbuffer3的值为:" + strbuffer3 + ", 容量为:" + strbuffer3.capacity() + ", 长度为:"
+ strbuffer3.length());
// 根据一个字符序列对象如stringbuffer来初始化一个stringbuilder对象
stringbuilder strbuilder3 = new stringbuilder(strbuffer2);
system.out.println("strbuilder3的值为:" + strbuilder3 + ", 容量为:" + strbuilder3.capacity() + ", 长度为:"
+ strbuilder3.length());
}
}
执行结果如下图所示:
- 拼接参数
拼接参数常用的方法方法如下图:
也就是说,该方法可以拼接所有的基本数据类型和其对应的包装类型,字符数组、字符序列对象及其他的引用对象等。
stringbuilder和stringbuffer的append
其示例代码如下所示:
public class stringtest {
public static void main(string[] args) throws ioexception {
// 可以拼接所有的基本数据类型
stringbuilder strbuilder = new stringbuilder();
stringbuffer strbuffer = new stringbuffer();
// 拼接int(byte、short都可以自动转换为int)
strbuilder.append(12).append(",");
strbuffer.append(12).append(",");
// 拼接long
strbuilder.append(13l).append(",");
strbuffer.append(13l).append(",");
// 拼接float
strbuilder.append(3.4f).append(",");
strbuffer.append(3.4f).append(",");
// 拼接double
strbuilder.append(3.5).append(",");
strbuffer.append(3.5).append(",");
// 拼接字符数组
strbuilder.append("hello".tochararray()).append(",");
strbuffer.append("hello".tochararray()).append(",");
// 拼接其他引用对象
strbuilder.append(new date()).append(",");
strbuffer.append(new date()).append(",");
// 拼接指定字符数组偏移指定位数后的指定长度字符
strbuilder.append("hello".tochararray(), 2, 2).append(",");
strbuffer.append("hello".tochararray(), 2, 2).append(",");
// 拼接指定字符序列对象(常见的为string、stringbuffer和stringbuilder)指定开始和结束(不包括)的字符串
strbuilder.append("hello", 1, 3).append(",");
strbuffer.append("hello", 1, 3).append(",");
printstrbuilder(strbuilder);
printstrbuffer(strbuffer);
}
private static void printstrbuilder(stringbuilder strbuilder) {
string[] strarr = strbuilder.deletecharat(strbuilder.length() - 1).tostring().split(",");
system.out.println("stringbuilder信息为:n" + arrays.aslist(strarr));
}
private static void printstrbuffer(stringbuffer strbuffer) {
string[] strarr = strbuffer.deletecharat(strbuffer.length() - 1).tostring().split(",");
system.out.println("stringbuffer信息为:n" + arrays.aslist(strarr));
}
}
只想结果如下图所示:
- 获取某个字符串在另一个字符串中的索引位置
这里使用的方法有四个,如下图:
相关的示例代码如下所示:
public class stringtest {
public static void main(string[] args) throws ioexception {
stringbuilder strbuilder = new stringbuilder("no zuo no die no happy no problem");
stringbuffer strbuffer = new stringbuffer("no zuo no die no happy no problem");
// indexof
system.out.println(""no"在strbuilder中首次出现的位置为:" + strbuilder.indexof("no"));
system.out.println(""no"在strbuffer中首次出现的位置为:" + strbuffer.indexof("no"));
system.out.println(""no"在strbuilder中在索引3之后首次出现的位置为:" + strbuilder.indexof("no", 3));
system.out.println(""no"在strbuffer中在索引3之后首次出现的位置为:" + strbuffer.indexof("no", 3));
// lastindexof
system.out.println(""no"在strbuilder中最后出现的位置为:" + strbuilder.lastindexof("no"));
system.out.println(""no"在strbuffer中最后出现的位置为:" + strbuffer.lastindexof("no"));
system.out.println(""no"在strbuilder中在索引20之前最后出现的位置为:" + strbuilder.lastindexof("no", 20));
system.out.println(""no"在strbuffer中在索引20之前最后出现的位置为:" + strbuffer.lastindexof("no", 20));
}
}
执行结果如下图所示:
- 插入方法
插入方法为:insert(int offset, xxx xxx), 目的是在偏移offset个字符后插入xxx。这里的xxx表示所有的基本数据类型及其对应的包装类型、字符数组、字符序列对象和其他的引用对象等。常用方法如下:
相关示例代码如下所示:
public class stringtest {
public static void main(string[] args) {
stringbuilder strbuilder = new stringbuilder("hello");
stringbuffer strbuffer = new stringbuffer("hello");
system.out.println("在strbuilder偏移2位后插入整数3的结果为:" + strbuilder.insert(2, 3));
system.out.println("在strbuffer偏移3位后插入整数3的结果为:" + strbuffer.insert(3, 3));
stringbuilder strbuilder2 = new stringbuilder("world");
stringbuffer strbuffer2 = new stringbuffer("world");
system.out.println("在strbuilder2偏移2位后插入'好'的结果为:" + strbuilder2.insert(2, '好'));
system.out.println("在strbuffer2偏移3位后插入'好'的结果为:" + strbuffer2.insert(3, '好'));
stringbuilder strbuilder3 = new stringbuilder("what");
stringbuffer strbuffer3 = new stringbuffer("what");
system.out.println("在strbuilder3偏移2位后插入4l的结果为:" + strbuilder3.insert(2, 4l));
system.out.println("在strbuffer3偏移3位后插入4l的结果为:" + strbuffer3.insert(3, 4l));
stringbuilder strbuilder4 = new stringbuilder("where");
stringbuffer strbuffer4 = new stringbuffer("where");
system.out.println("在strbuilder4偏移2位后插入3.14f的结果为:" + strbuilder4.insert(2, 3.14f));
system.out.println("在strbuffer4偏移3位后插入3.14f的结果为:" + strbuffer4.insert(3, 3.14f));
stringbuilder strbuilder5 = new stringbuilder("when");
stringbuffer strbuffer5 = new stringbuffer("when");
system.out.println("在strbuilder5偏移2位后插入1.414的结果为:" + strbuilder5.insert(2, 1.414));
system.out.println("在strbuffer5偏移3位后插入1.414的结果为:" + strbuffer5.insert(3, 1.414));
stringbuilder strbuilder6 = new stringbuilder("crazy");
stringbuffer strbuffer6 = new stringbuffer("crazy");
system.out.println("在strbuilder6偏移2位后插入true的结果为:" + strbuilder6.insert(2, true));
system.out.println("在strbuffer6偏移3位后插入false的结果为:" + strbuffer6.insert(3, false));
stringbuilder strbuilder7 = new stringbuilder("hehe");
stringbuffer strbuffer7 = new stringbuffer("hehe");
system.out.println("在strbuilder7偏移2位后插入date的结果为:" + strbuilder7.insert(2, new date()));
system.out.println("在strbuffer7偏移3位后插入date的结果为:" + strbuffer7.insert(3, new date()));
stringbuilder strbuilder8 = new stringbuilder("this");
stringbuffer strbuffer8 = new stringbuffer("this");
system.out.println("在strbuilder8偏移2位后插入字符数组['a', 'r', 'e']的结果为:"
+ strbuilder8.insert(2, new char[]{'a', 'r', 'e'}));
system.out.println("在strbuffer8偏移3位后插入字符数组['a', 'r', 'e']的结果为:"
+ strbuffer8.insert(3, new char[]{'a', 'r', 'e'}));
stringbuilder strbuilder9 = new stringbuilder("happend");
stringbuffer strbuffer9 = new stringbuffer("happend");
system.out.println("在strbuilder9偏移2位后插入date的结果为:"
+ strbuilder9.insert(2, new stringbuffer("234")));
system.out.println("在strbuffer9偏移3位后插入date的结果为:"
+ strbuffer9.insert(3, new stringbuilder("234")));
stringbuilder strbuilder10 = new stringbuilder("that");
stringbuffer strbuffer10 = new stringbuffer("that");
system.out.println("在strbuilder10偏移2位后插入字符数组['a', 'r', 'e']的结果为:"
+ strbuilder10.insert(2, new char[]{'a', 'r', 'e'}, 0, 2));
system.out.println("在strbuffer10偏移3位后插入字符数组['a', 'r', 'e']的结果为:"
+ strbuffer10.insert(3, new char[]{'a', 'r', 'e'}, 0, 2));
stringbuilder strbuilder11 = new stringbuilder("jerry");
stringbuffer strbuffer11 = new stringbuffer("jerry");
system.out.println("在strbuilder11偏移2位后插入date的结果为:"
+ strbuilder11.insert(2, new stringbuffer("234"), 0, 2));
system.out.println("在strbuffer11偏移3位后插入date的结果为:"
+ strbuffer11.insert(3, new stringbuilder("234"), 0, 2));
}
}
执行结果如下图所示:
- 删除某个或某些字符
删除某个或某些的字符方法如下图所示:
相关示例代码如下:
public class stringtest {
public static void main(string[] args) {
stringbuilder strbuilder = new stringbuilder("hello");
stringbuffer strbuffer = new stringbuffer("hello");
system.out.println("strbuilder删除索引为1处的字符后结果为:" + strbuilder.deletecharat(1));
system.out.println("strbuffer删除索引为1处的字符后结果为:" + strbuffer.deletecharat(1));
stringbuilder strbuilder2 = new stringbuilder("hello");
stringbuffer strbuffer2 = new stringbuffer("hello");
system.out.println("strbuilder2删除索引从1到3(不包括3)的字符后结果为:" + strbuilder2.delete(1, 3));
system.out.println("strbuffer2删除索引从1到3(不包括3)的字符后结果为:" + strbuffer2.delete(1, 3));
}
}
执行结果如下图所示:
- 取子字符串
取子字符串的方法如下:
示例代码如下所示:
public class stringtest {
public static void main(string[] args) {
stringbuilder strbuilder = new stringbuilder("hello world");
stringbuffer strbuffer = new stringbuffer("hello world");
system.out.println("strbuilder从索引3处开始到字符串末尾的子字符串为:" + strbuilder.substring(3));
system.out.println("strbuffer从索引3处开始到字符串末尾的子字符串为:" + strbuffer.substring(3));
stringbuilder strbuilder2 = new stringbuilder("hello world");
stringbuffer strbuffer2 = new stringbuffer("hello world");
system.out.println("strbuilder从索引3处开始到5(不包括5)的子字符串为:" + strbuilder.substring(3, 5));
system.out.println("strbuffer从索引3处开始到5(不包括5)的子字符串为:" + strbuffer.substring(3, 5));
}
}
执行结果如下图所示:
- 其他
除了以上列举的方法外,还有一些常用的方法,分别为:
- int capacity():获取容量(初始化字符数组的长度)
- int length():获取长度(实际字符的长度)
- replace(int start, int end, string str):将索引从start到end(不包括end)的字符序列替换为str
- char charat(int index):获取指定索引出的字符
- void setcharat(int index, char ch):用ch替换指定索引处的字符
- void setlength(int newwlength):将字符序列强制变为指定长度,多余的字符被置为null。
- charsequence subsequence(int start, int end):获取子字符序列对象。
- reverse():将字符序列进行反转。
示例代码如下所示:
public class stringtest {
public static void main(string[] args) {
stringbuilder strbuilder = new stringbuilder("hello world");
stringbuffer strbuffer = new stringbuffer("hello world");
// 获取字符容量
system.out.println("strbuilder的容量为:" + strbuilder.capacity());
system.out.println("strbuffer的容量为:" + strbuffer.capacity());
// 获取长度
system.out.println("strbuilder的长度为:" + strbuilder.length());
system.out.println("strbuffer的长度为:" + strbuffer.length());
// 替换字符串
system.out.println("用"tom"替换strbuilder的0到5(不包括5)后结果为:"
+ strbuilder.replace(0, 5, "tom"));
system.out.println("用"tom"替换strbuffer的0到5(不包括5)后结果为:"
+ strbuffer.replace(0, 5, "tom"));
// 获取指定索引处的字符
system.out.println("strbuilder的索引为1的字符为:" + strbuilder.charat(1));
system.out.println("strbuffer的索引为1的字符为:" + strbuffer.charat(1));
// 将字符序列强制变为指定长度
strbuilder.setlength(3);
system.out.println("strbuilder强制变为长度为3的结果为:" + strbuilder);
strbuffer.setlength(3);
system.out.println("strbuffer强制变为长度为3的结果为:" + strbuffer);
// 取子字符序列
system.out.println("strbuilder的从0到2的子字符序列为:" + strbuilder.subsequence(0, 2));
system.out.println("strbuffer的从0到2的子字符序列为:" + strbuffer.subsequence(0, 2));
// 字符序列反转
system.out.println("strbuilder的反转后为:" + strbuilder.reverse());
system.out.println("strbuffer的反转为:" + strbuffer.reverse());
}
}
执行结果如下图所示:
自此,关于stringbuffer和stringbuilder的介绍就已经算是结束了。
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