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shy-coder
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JavaDaily
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‎.gitignore

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# Compiled class file
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*.class
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# Log file
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*.log
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# BlueJ files
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*.ctxt
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# Mobile Tools for Java (J2ME)
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.mtj.tmp/
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# Package Files #
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*.jar
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*.war
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*.nar
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*.ear
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*.zip
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*.tar.gz
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*.rar
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# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
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hs_err_pid*

‎JavaDaily.iml

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<?xml version="1.0" encoding="UTF-8"?>
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<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_8">
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<output url="file://$MODULE_DIR$/target/classes" />
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<output-test url="file://$MODULE_DIR$/target/test-classes" />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
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<sourceFolder url="file://$MODULE_DIR$/src/main/resources" type="java-resource" />
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<sourceFolder url="file://$MODULE_DIR$/src/test/java" isTestSource="true" />
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<excludeFolder url="file://$MODULE_DIR$/target" />
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</content>
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<orderEntry type="jdk" jdkName="1.8" jdkType="JavaSDK" />
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<orderEntry type="sourceFolder" forTests="false" />
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<orderEntry type="library" name="Maven: junit:junit:4.13" level="project" />
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<orderEntry type="library" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
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<orderEntry type="library" name="Maven: org.projectlombok:lombok:1.18.14" level="project" />
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</component>
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</module>

‎pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>code</artifactId>
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<groupId>groupId</groupId>
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<version>1.0-SNAPSHOT</version>
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<relativePath>../code/pom.xml</relativePath>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.shy</groupId>
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<artifactId>JavaDaily</artifactId>
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</project>

‎src/main/java/com/shy/day01/BubbleSort.java

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package com.shy.day01;
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/**
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* @ClassName BubbleSort
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* @Description TODO
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* @Author shy
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* @Date 2020/10/20
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**/
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public class BubbleSort {
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public static void bubbleSort1(int[]a,int n){
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int i,j;
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for ( i = 0; i <n ; i++) {
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for ( j = 1; j <n-i ; j++) {
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if (a[j-1]>a[j]){
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int temp;
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temp =a[j-1];
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a[j-1]=a[j];
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a[j]=temp;
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}
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}
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}
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}
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public static void main(String[] args) {
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int[] arr={1,2,6,3,12,31,13,1};
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BubbleSort.bubbleSort1(arr,arr.length);
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for (int i:arr){
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System.out.print(i+",");
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}
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}
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}

‎src/main/java/com/shy/day02/StringTest01.java

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package com.shy.day02;
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/**
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* @ClassName StringTest01
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* @Description TODO
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* @Author shy
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* @Date 2020/10/21
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**/
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public class StringTest01 {
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public static void main(String[] args) {
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//创建一个"abc"字符串对象，该对象的内存地址，让s1变量保存
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//s1是一个引用，s1指向"abc"对象
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String s1 = "abc";
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//可以让s1重新指向
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//但是"def"字符串本身不可变
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s1 = "def";
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//在字符串常量池中新建一个"hello"字符串对象，该对象不可变
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String s2 = "hello";
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//从字符串常量池中直接拿来用
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String s3 = "hello";
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//判断字符串是否相等不能用==
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System.out.println(s2 == s3);
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String s4 = new String("abc");
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System.out.println(System.identityHashCode(s4));
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String s5 = new String("abc");
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System.out.println(System.identityHashCode(s5));
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System.out.println(s4 == s5);
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//以下程序在执行结束后，会在字符串常量池中创建三个字符串对象"aaa""bbb""aaabbb"
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String s6 = "aaa";
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String s7 = "bbb";
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String s8 = s6 + s7;
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}
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}

‎src/main/java/com/shy/day02/StringTest02.java

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package com.shy.day02;
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/**
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* @ClassName StringTest01
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* @Description TODO
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* @Author shy
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* @Date 2020/10/21
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**/
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public class StringTest02 {
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public static void main(String[] args) {
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String s1 = "abc";
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String s2 = new String("abc");
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byte[] bytes = {97,98,99,100};
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String s3 = new String(bytes);
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//String已经重写了Object中的toString方法
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System.out.println(s3);
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//1代表下标，2代表长度
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String s4 = new String(bytes,1,2);
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System.out.println(s4);
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char[] c1 = {'我','是','中','国','人',};
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String s5 = new String(c1);
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System.out.println(s5);
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String s6 = new String(c1,2,2);
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System.out.println(s6);
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}
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}

‎src/main/java/com/shy/day03/StringTest.java

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package com.shy.day03;
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import java.util.Scanner;
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/**
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* @ClassName StringTest
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* @Description TODO
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* @Author shy
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* @Date 2020/10/22
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**/
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public class StringTest {
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public static void main(String[] args) {
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//获取键盘输入并赋值给S1字符串
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Scanner s1 = new Scanner(System.in);
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System.out.println("请给字符串a赋值");
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String a = s1.nextLine();
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Scanner s2 = new Scanner(System.in);
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System.out.println("请给字符串b赋值");
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String b = s2.nextLine();
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System.out.println("字符串a的内容为："+ a);
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System.out.println("字符串a的内容为："+ b);
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//将两个字符串比较是否相同
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System.out.println("两字符串的内容是否相同?"+a.equals(b));
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//比较两字符串是否同一个对象
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System.out.println(a == b);
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//比较两个字符串的内容是否相同
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System.out.println(a.equals(b));
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//比较两个字符串（忽略大小写）
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System.out.println(a.equalsIgnoreCase(b));
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//将两个字符串相加合成为一个新字符串
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String c = a + b;
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System.out.println("字符串a与b合并之后的内容为："+c);
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//查找某一子字符串是否被包含在此字符串之中，如果包含，包含了多少次
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Scanner s3 = new Scanner(System.in);
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System.out.println("请输入想要查找的字符串：");
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String d = s3.nextLine();
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//子字符串是否被包含在此字符串之中，包含输出true，否则输出false
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boolean con = c.contains(d);
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System.out.println("子字符串是否被包含在此字符串之中："+con);
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//调用count,输出包含次数
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System.out.println("包含次数为："+repetitions(c,d));
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//把此子字符串替换为其他的新的指定字符串
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Scanner s4 = new Scanner(System.in);
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System.out.println("请选择是否替换字符(串)：确定（1）/拒绝（2）");
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int e = s4.nextInt();
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switch (e){
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case 1:
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Scanner s5 = new Scanner(System.in);
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System.out.println("请输入想逃替换的的原字符");
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String f = s5.nextLine();
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Scanner s6 = new Scanner(System.in);
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System.out.println("请输入想逃替换的的原字符");
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String g = s6.nextLine();
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//将f替换为g
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String z = c.replace(f,g);
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System.out.println("替换前："+c);
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System.out.println("替换后："+z);
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break;
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case 2:
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System.out.println("最终的字符串内容为：\n"+c);
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break;
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default:
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System.out.println("该字符（串）有误");
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break;
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}
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}
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public static int repetitions(String c,String d){
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//创建repetitions统计出现次数
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//创建一个计数器，统计次数
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int count = 0;
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//创建计数器，设开始的地址
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int fromIndex = 0;
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while ((fromIndex = c.indexOf(d,fromIndex)) != -1){
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//子串第一次出现的位置+长度=下一次的起始位置
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fromIndex = fromIndex + d.length();
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count++;
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}
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return count;
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}
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}

‎src/main/java/com/shy/day04/ArraysDemo.java

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package com.shy.day04;
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import java.util.Arrays;
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/**
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* @ClassName ArraysDemo
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* @Description Arrays练习
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* @Author shy
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* @Date 2020/10/23
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* java.util.Arrays是一个与数组相关的工具类，里面提供了大量静态方法，用来实现数组常见的操作
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* public static String toString(数组)：将参数数组变成字符串(按照默认格式：[元素1,元素2,元素3...])
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* public static String sort(数组)：按照默认升序(从小到大)对数组的元素进行排序
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*备注：
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* 1.如果是数值，sort默认按照升序从小到大
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* 2.如果是字符串，sort默认按照字母排序
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* 3.如果是自定义的类型，那么这个自定义的类型需要有Comparable或者Comparator接口的支持
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**/
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public class ArraysDemo {
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public static void main(String[] args) {
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int[] intArray = {10,20,30};
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//将int[]数组按照默认格式变成字符串
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String intStr = Arrays.toString(intArray);
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System.out.println(intStr);
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//对整型数组排序
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int[] array1 = {2,1,3,7,9};
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Arrays.sort(array1);
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System.out.println(Arrays.toString(array1));
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//对字符串数组排序
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String[] array2 = {"aaa","ccc","bbb"};
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Arrays.sort(array2);
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System.out.println(Arrays.toString(array2));
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//将一个随机字符串中的所有字符升序排列，并倒序打印
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String str = "adsad3123fa";
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//如何进行升序排列：sort
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//必须是一个数组，才能用Arrays.sort方法
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//String-->数组，用toCharArray
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char[] chars = str.toCharArray();
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//对字符数组进行升序排序
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Arrays.sort(chars);
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//倒叙遍历
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for (int i = chars.length-1; i >= 0; i--){
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System.out.print(chars[i] + " ");
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}
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}
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}

‎src/main/java/com/shy/day04/MathDemo.java

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package com.shy.day04;
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/**
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* @ClassName MathDemo
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* @Description Math练习
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* @Author shy
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* @Date 2020/10/23
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* java.util.Math类是数学县官的工具类，里面提供了大量的静态方法，完成与数学运算相关的操作
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* public static double abs(double num):获取绝对值，有多种重载
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* public static double ceil(double num):向上取整
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* public static double floor(double num):向下取整
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* public static double round(double num):四舍五入
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* Math.PI代表近似的圆周率常量(double)
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**/
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public class MathDemo {
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public static void main(String[] args) {
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//获取绝对值
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System.out.println(Math.abs(3.14));
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System.out.println(Math.abs(0));
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System.out.println(Math.abs(-2.5));
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System.out.println("-----------------------");
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//向上取整
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System.out.println(Math.ceil(3.9));
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System.out.println(Math.ceil(3.1));
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System.out.println(Math.ceil(3.0));
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System.out.println("-----------------------");
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//向下取整，抹零
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System.out.println(Math.floor(30.1));
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System.out.println(Math.floor(30.9));
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System.out.println(Math.floor(31.0));
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System.out.println("-----------------------");
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//四舍五入
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System.out.println(Math.round(20.4));
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System.out.println(Math.round(30.5));
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//计算在-10.8到5.9之间，绝对值大于6或者小于2.1的整数有多少个？
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int count = 0;
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double min = -10.8;
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double max = 5.9;
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//这样处理，变量i就是区间之内所有的整数
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for (int i = (int) min; i < max; i++){
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int abs = Math.abs(i);
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if (abs > 6 || abs < 2.1){
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System.out.print(i + " ");
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count++;
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}
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}
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System.out.println("总共有："+ count + "个");
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}
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}

‎src/main/java/com/shy/day04/MyClass.java

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package com.shy.day04;
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/**
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* @ClassName MyClass
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* @Description 成员变量、静态变量、成员方法、静态方法
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* @Author shy
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* @Date 2020/10/23
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**/
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public class MyClass {
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//成员变量
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int num;
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//静态变量
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static int numStatic;
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/**
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* 成员方法
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*/
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public void method() {
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System.out.println("这是一个成员方法");
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//成员方法可以访问成员变量
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System.out.println(num);
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//成员方法可以访问静态变量
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System.out.println(numStatic);
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}
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/**
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* 静态方法
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*/
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public static void methodStatic() {
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System.out.println("这是一个静态方法");
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//静态方法可以访问静态变量
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System.out.println(numStatic);
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//静态不能直接访问非静态（重点）
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//System.out.println(num); 错误写法
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//静态方法中不能使用this关键字
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//System.out.println(this); X
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}
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}

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