标签:ignore 顺序 效率 重载方法 case += 相同 常量 counter
三个字符串类
空字符串不是null,空字符串分配了空间,而null没有分配空间
不可变字符串的创建
package chapter8;
public class chapt01 {
public static void main(String[] args) {
// 创建字符串对象
String s1 = "";
String s2 = new String("hello world");
char[] chars = {‘a‘,‘b‘,‘c‘,‘d‘};
String s3 = new String(chars);
byte[] bytes = {97,98,99};
String s4 = new String(bytes);
String s5 = new String(chars,1,2);
}
}
package chapter8;
import java.util.Date;
public class chapt02 {
public static void main(String[] args) {
String s1 = "hello ";
s1 += "world";
String s2 = "Hello";
s2 = s2.concat(" ").concat("World");
Date time = new Date();
System.out.println(s1);
System.out.println(s2);
// 对象拼接自动采用toString()方法
System.out.println("Today is " + time);
}
}
package chapter8;
public class chapt03 {
public static void main(String[] args) {
String sourceStr = "this is a string accessing example";
int firstChar = sourceStr.indexOf(‘r‘);
int secondChar = sourceStr.indexOf(‘r‘,20);
// 表达式的值从索引值为20开始往后面搜索
int firstString = sourceStr.indexOf("is");
int secondString = sourceStr.indexOf("is",5);
int lastChar1 = sourceStr.lastIndexOf(‘r‘);
int lastChar2 = sourceStr.lastIndexOf(‘r‘,5);
int lastString1 = sourceStr.lastIndexOf("is");
int lastString2 = sourceStr.lastIndexOf("is",2);
int length = sourceStr.length();
}
}
package chapter8;
public class chapt04 {
public static void main(String[] args) {
String s1 = new String("hello");
String s2 = new String("hello");
String s3 = new String("HELLO");
// 比较两个字符串的内容是否相同 true
System.out.println(s1.equals(s2));
// 比较两个字符串是否为相同的引用 false
System.out.println(s1 == s2);
// 忽略大小写的情况 false true
System.out.println(s1.equals(s3));
System.out.println(s1.equalsIgnoreCase(s3));
String s4 = new String("python");
String s5 = new String("java");
String s6 = new String("go");
// 比较两个字符串的大小
// s5 < s4 返回小于0的数字 , s5 > s6 返回大于零的数字
System.out.println(s5.compareTo(s4));
System.out.println(s5.compareTo(s6));
// 忽略大小写的字符串比较 返回值为0
System.out.println(s4.compareToIgnoreCase("PYTHON"));
// 比较前缀和后缀
String[] fileFolder = {"java.doc","python.xls","hello.xls","go.doc","html.doc"};
int wordCounter = 0;
for(String file : fileFolder){
file = file.trim();
if(file.endsWith(".doc")) {
wordCounter++;
}
}
int xlsCounter = 0;
for (String file : fileFolder){
file = file.trim();
if (file.endsWith(".xls")){
xlsCounter++;
}
}
System.out.println("文档数量是:" + wordCounter);
System.out.println("表格数量是:" + xlsCounter);
}
}
package chapter8;
public class chapt05 {
public static void main(String[] args) {
String sourceStr = new String("There is a string accessing example");
String subStr1 = sourceStr.substring(28);
String substr2 = sourceStr.substring(11,17);
// %n是换行的格式字符串,只能用于print输出语句当中
// \n也是换行的转义字符,可用于任何字符串
System.out.printf("subStr1 == %s%n",subStr1);
System.out.printf("subStr2 == %s%n",substr2);
// 分割字符串
String[] array = sourceStr.split(" ");
System.out.println("调用Split()方法....");
for (String item : array){
System.out.printf("%s%n",item);
}
}
}
package chapter8;
public class chapt06 {
public static void main(String[] args) {
StringBuilder builder1 = new StringBuilder();
System.out.println("length == " + builder1.length());
System.out.println("capacity == " + builder1.capacity());
StringBuilder builder2 = new StringBuilder("hello");
System.out.println("length == " + builder2.length());
System.out.println("capacity == " + builder2.capacity());
}
// 缓冲区的默认长度为16,超过容量会自动扩容
StringBuilder builder3 = new StringBuilder();
}
package chapter8;
public class chapt07 {
public static void main(String[] args) {
StringBuilder s1 = new StringBuilder("Hello");
s1.append(" ").append("world");
s1.append(".");
System.out.println(s1);
// 添加布尔值 空对象 转义符
StringBuilder s2 = new StringBuilder();
Object object = null;
// 布尔值false转换为"false" , null转换为"null"
s2.append(false).append(‘\t‘).append(object);
System.out.println(s2);
// 添加数值
StringBuilder s3 = new StringBuilder();
for (int i = 0;i < 10; i++){
s3.append(i);
}
System.out.println(s3);
}
}
package chapter8;
public class chapt08 {
public static void main(String[] args) {
String str1 = "Java C";
StringBuilder mstr = new StringBuilder(str1);
// 插入字符串
mstr.insert(4," C++");
System.out.println(mstr);
// 追加字符串
mstr.insert(mstr.length()," Python");
mstr.append(" PHP");
System.out.println(mstr);
// 删除字符串
mstr.delete(11,23);
System.out.println(mstr);
}
}
标签:ignore 顺序 效率 重载方法 case += 相同 常量 counter
原文地址:https://www.cnblogs.com/Tang0706/p/14676449.html