String ,StringBuffer,StringBuilder
package Day12_22_00;
import java.util.Arrays;
import java.util.Comparator;
//最具逼格的冒泡排序
public class Test002
{
/*
* 泛型（generic）-让类型不再是程序中的硬代码（hard code）
*
* <T extends Comparable<T>>--T代表的是引用类型，不是基本类型 此处的extends不是继承，
* 而是泛型限定. 限定T的类型必须是Comparable接口的子类型
*
*/
public static <T extends Comparable<T>> void bubbleSort(T[] array)
{
// 通用冒泡排序
boolean swapped = true;
for (int i = 1; swapped && i < array.length; i++)
{
swapped = false;
for (int j = 0; j < array.length - i; j++)
{
if (array[j].compareTo(array[j + 1]) > 0)
{
T temp = array[j];
array[j] = array[j + 1];
array[j + 1] = temp;
swapped = true;
}
}
}
}
public static <T> void bubbleSort(T[] array,Comparator<T> comp)
{
// 通用冒泡排序
boolean swapped = true;
for (int i = 1; swapped && i < array.length; i++)
{
swapped = false;
for (int j = 0; j < array.length - i; j++)
{
if (comp.compare(array[j], array[j+1])>0)
{
T temp = array[j];
array[j] = array[j + 1];
array[j + 1] = temp;
swapped = true;
}
}
}
}
public static void main(String[] args)
{
Double[] aa =
{ 1.0, 34., 5., 7., 3., 98., 54. };
Student[] stu =
{
new Student("汪汪汪", 17),
new Student("喵喵喵", 45),
new Student("王焕琪", 23)
};
bubbleSort(stu);
System.out.println(Arrays.toString(stu));
// bubbleSort(stu,new Comparator<Student>()
// {
//
// @Override
// public int compare(Student o1, Student o2)
// {
// return o1.getAge()-o2.getAge();
// }
// });
//lambda表达式
bubbleSort(stu, (o1,o2)->{
return o1.getAge()-o2.getAge();
});
System.out.println(Arrays.toString(stu));
bubbleSort(aa);
System.out.println(Arrays.toString(aa));
}
}
class Student implements Comparable<Student>
{
private int age;
private String name;
public Student(String name, int age)
{
this.age = age;
this.name = name;
}
@Override
public String toString()
{
return name + ":" + age;
}
@Override
public int compareTo(Student o)
{
return -this.name.compareTo(o.name);
}
public int getAge()
{
return age;
}
}
跑马灯
package Day12_23_00;
import java.awt.Font;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.Timer;
@SuppressWarnings("serial")
public class Demo_001 extends JFrame
{
String string="欢迎来到千锋 ************";
public Demo_001()
{
this.setTitle("");
this.setSize(300, 100);
this.setLocationRelativeTo(null);
this.setResizable(false);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
JLabel jLabel=new JLabel(string);
jLabel.setFont(new Font("微软雅黑",Font.PLAIN,25));
this.add(jLabel);
Timer timer=new Timer(500, e->{
string="fadsfa";
string=string.substring(1)+string.charAt(0);
jLabel.setText(string);
});
timer.start();
}
public static void main(String[] args)
{
new Demo_001().setVisible(true);
}
}
package Day12_23_00;
/*
* String是不变字符串，对字符串操作会创建新的字符串对象
* StringBuffer和StringBuilder代表可变字符串
* 对字符串修改时，不会创建新的字符串对象
* StringBuffer是线程安全的-多个线程可以操作同一个StringBuffer对象
* StringBuilder-是线程不安全的-多个线程同时操作一个StringBuilder时会发生错误
* StringBuider是java5引入的可变字符串类型 他拥有比StringBuffer更好的性能
*
* 如果要频繁的修改一个字符串请不要使用String，因为每次修改都可能创建新的字符串对象，
* 所以在这种场景下（时间消耗实验）应该使用StringBuffer或者StringBuilder
*/
public class Test002
{
public static void main(String[] args)
{
StringBuffer sb=new StringBuffer("hello");
//append()-在字符串末尾追加新的内容
sb.append("world!");
sb.append(" goodbye");
//insert()-从指定位置插入新内容
sb.insert(5,"good");
sb.insert(0, "hi!");
System.out.println(sb);
//deletCharAt()-删除指定位置字符
sb.deleteCharAt(10);
sb.delete(0, 9);
System.out.println(sb);
//reverse()-字符串反转
sb.reverse();
System.out.println(sb);
//setCharAt()-修改指定位置的字符
sb.setCharAt(3, '#');
System.out.println(sb);
}
}
正则表达式--regular expression
package Day12_23_01;
//正则表达式-regular expression
/*
* 定义字符串的匹配模式
*/
public class Test003
{
public static void main(String[] args)
{
//验证手机号码是否合法
String str="12545466772";
boolean isValid= str.matches("1[3478][0-9]{9}");//[0-9]-->\\d
System.out.println(isValid);
//验证QQ号是否合法
String qqid="5345443896786788789";
boolean isValidQQ=qqid.matches("[1-9]\\d{4,11}");//不设上限{4,}
System.out.println(isValidQQ);
//验证用户名
String username="dfafkj345435";
boolean isValidusernaem=username.matches("[a-zA-Z0-9_]{6,20}");
//[^a-zA-Z0-9_]可用\\W-->不能是字母数字下划线
System.out.println(isValidusernaem);
//文字马赛克
String msg="操你大爷，日你大爷，干你大爷，fuck你大爷";
msg=msg.replaceAll("[^操干日]|[fF]\\s*[Uu]\\s*[Cc]\\s*[Kk]", "*");
System.out.println(msg);
}
}
创建正则表达式Pattern
package Day12_23_01;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
//创建正则表达式Pattern
public class Test004
{
public static void main(String[] args)
{
boolean ismatchs=Pattern.matches("\\w{6,10}", "jdfadlfjkad");
System.out.println(ismatchs);
Pattern pattern=Pattern.compile("\\w{6,20}");
Matcher matcher=pattern.matcher("jeckfroud");
System.out.println(matcher.matches());
Pattern pattern2=Pattern.compile("a*b",Pattern.CASE_INSENSITIVE);
Matcher matcher2=pattern2.matcher("qrqerqwabbaABABbaBaaabaabaaab");
while (matcher2.find())
{
System.out.println(matcher2.group());
}
}
}
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