Java基础
1.冒泡排序
public static void main ( String [ ] args) {
int [ ] intAr = { 3 , 2 , 1 , 5 , 6 , 4 , 2 , 1 , 8 } ;
bubbleSort ( intAr) ;
System . out. println ( getArrStr ( intAr) ) ;
}
public static int [ ] bubbleSort ( int [ ] intArr) {
for ( int i = 0 ; i < intArr. length - 1 ; i++ ) {
for ( int j = 0 ; j < intArr. length - i - 1 ; j++ ) {
if ( intArr[ j] > intArr[ j + 1 ] ) {
int tmp = intArr[ j + 1 ] ;
intArr[ j + 1 ] = intArr[ j] ;
intArr[ j] = tmp;
}
}
}
return intArr;
}
2.二分查找
public static void main ( String [ ] args) {
int [ ] intAr = { 3 , 2 , 1 , 5 , 6 , 4 , 2 , 1 , 8 } ;
int index = binarySearch ( intAr, 0 ) ;
System . out. println ( "获取到下标:" + index) ;
}
public static int binarySearch ( int [ ] intArr, int search) {
int startIndex = 0 ;
int endIndex = intArr. length - 1 ;
while ( startIndex <= endIndex) {
int mid = ( startIndex + endIndex) / 2 ;
if ( intArr[ mid] == search) {
return mid;
} else if ( intArr[ mid] < search) {
startIndex = mid + 1 ;
} else {
endIndex = mid - 1 ;
}
}
return - 1 ;
}
3. class(类)
public static void main ( String [ ] args) {
Person person = new Person ( ) ;
person. name = "许康杰" ;
person. age = 20 ;
System . out. println ( person. name) ;
System . out. println ( person. age) ;
System . out. println ( person. eat ( "金针菇" ) ) ;
person. play ( ) ;
Person person2 = new Person ( ) ;
person2. name = "李国涛" ;
person2. age = 18 ;
System . out. println ( person2. name) ;
System . out. println ( person2. age) ;
Person person3 = person2;
System . out. println ( person3. name) ;
System . out. println ( person3. age) ;
useVar ( ) ;
}
public static void useVar ( ) {
{
int var = 10 ;
System . out. println ( var ) ;
}
}
Person 类:
public class Person {
String name;
int age;
double high;
double weight;
String gender;
public String eat ( String food) {
System . out. println ( food+ "被消化了一部分" ) ;
return "消化过的食物" ;
}
public void drink ( String drink) {
System . out. println ( "人类可以喝饮料..." ) ;
}
public void play ( ) {
System . out. println ( "人类可以玩游戏..." ) ;
}
}
4.参数传递
public static void main ( String [ ] args) {
Person person = new Person ( ) ;
person. name = "易政" ;
usePerson ( person) ;
System . out. println ( person. name) ;
System . out. println ( person. age) ;
usePerson ( new Person ( ) ) ;
}
public static void usePerson ( Person inPerson) {
System . out. println ( inPerson) ;
inPerson. name = "汪雨" ;
inPerson. age = 18 ;
}
5.封装
public static void main ( String [ ] args) {
Student student = new Student ( ) ;
student. setName ( "李四" ) ;
student. setAge ( 18 ) ;
student. setGender ( "不知道" ) ;
student. printInfo ( ) ;
System . out. println ( student. getName ( ) ) ;
System . out. println ( student. getAge ( ) ) ;
Phone phone = new Phone ( ) ;
phone. setNumber ( "183****8888" ) ;
phone. setUser ( "王五" ) ;
System . out. println ( phone. getUser ( ) ) ;
System . out. println ( phone. getNumber ( ) ) ;
}
Student 类:
public class Student {
private String name;
private int age;
private String gender;
public void setName ( String inName) {
name = inName;
}
public void setAge ( int age) {
this . age = age;
}
public void setGender ( String inGender) {
if ( inGender. equals ( "男" ) || inGender. equals ( "女" ) ) {
gender = inGender;
} else {
System . out. println ( "性别只能为男或女,您输入的信息不正确..." ) ;
}
}
public int getAge ( ) {
return age;
}
public String getName ( ) {
return name;
}
public String getGender ( ) {
return gender;
}
public void printInfo ( ) {
System . out. println ( "我叫:" + name + " 今年:" + age + " 性别是:" + gender) ;
}
}
6.构造方法
public static void main ( String [ ] args) {
Phone phone = new Phone ( ) ;
phone. setNumber ( "183****8888" ) ;
phone. setUser ( "陆玉龙" ) ;
System . out. println ( phone. getUser ( ) ) ;
System . out. println ( phone. getNumber ( ) ) ;
Phone phone2 = new Phone ( "袁枫" , "166****6666" ) ;
System . out. println ( phone2. getUser ( ) ) ;
System . out. println ( phone2. getNumber ( ) ) ;
Phone phone3 = new Phone ( "汪雨" ) ;
System . out. println ( phone3. getUser ( ) ) ;
System . out. println ( phone3. getNumber ( ) ) ;
phone2. call ( "188****8888" ) ;
Phone phone4 = new Phone ( "袁枫女朋友" , "188****8888" ) ;
phone2. call ( phone4) ;
useStaticPhone ( phone2) ;
}
public void usePhone ( Phone phone) {
System . out. println ( "手机号:" + phone. getNumber ( ) + "正在被使用..." ) ;
}
public static void useStaticPhone ( Phone phone) {
System . out. println ( "Demo05中的代码:" + "手机号:" + phone. getNumber ( ) + "正在被使用..." ) ;
}
phone类:
public class Phone {
public Phone ( ) {
System . out. println ( "这是Phone的构造方法..." ) ;
}
public Phone ( String user, String number) {
this . user = user;
this . number = number;
System . out. println ( "这是两个参数的Phone的构造方法..." ) ;
}
public Phone ( String user) {
this ( user, "111****0000" ) ;
System . out. println ( "这是1个参数的Phone的构造方法..." ) ;
}
private String user;
private String number;
public String getUser ( ) {
return user;
}
public void setUser ( String user) {
this . user = user;
}
public String getNumber ( ) {
return number;
}
public void setNumber ( String number) {
this . number = number;
}
public void call ( String number) {
System . out. println ( this . number + "正在打电话给" + number) ;
}
public void call ( Phone phone) {
System . out. println ( this . user + "\t" + this . number + "正在打电话给" + phone. user + "\t" + phone. number) ;
}
public void show ( ) {
System . out. println ( "当前用户为:" + user+ "其手机号码为:" + number) ;
}
}
7.成员方法
public class Demo06UseObjectFunction {
public static void main ( String [ ] args) {
Phone phone2 = new Phone ( "袁枫" , "166****6666" ) ;
System . out. println ( phone2. getUser ( ) ) ;
System . out. println ( phone2. getNumber ( ) ) ;
Demo06UseObjectFunction demo06UseObjectFunction = new Demo06UseObjectFunction ( ) ;
demo06UseObjectFunction. usePhone ( phone2) ;
useStaticPhone ( phone2) ;
Demo05GetObject . useStaticPhone ( phone2) ;
demo06UseObjectFunction. useStaticPhone ( phone2) ;
phone2. show ( ) ;
}
public void usePhone ( Phone phone) {
System . out. println ( "手机号:" + phone. getNumber ( ) + "正在被使用..." ) ;
}
public static void useStaticPhone ( Phone phone) {
System . out. println ( "Demo06中的代码:" + "手机号:" + phone. getNumber ( ) + "正在被使用..." ) ;
}
}
8. static
package com. shujia. Day04_packaging ;
public class Demo07StaticVar {
static int value;
static int data = 20 ;
int var = 1 ;
public static void main ( String [ ] args) {
Demo07StaticVar . value = 10 ;
System . out. println ( value) ;
System . out. println ( data) ;
useVar ( ) ;
new Demo07StaticVar ( ) . objectVar ( ) ;
Per per1 = new Per ( "张三" , "美国" ) ;
per1. show ( ) ;
Per per2 = new Per ( "李四" , "中国" ) ;
per2. show ( ) ;
per1. show ( ) ;
}
public static void useVar ( ) {
System . out. println ( "获取到Value:" + value) ;
System . out. println ( "获取到data:" + data) ;
}
public void objectVar ( ) {
var = 10 ;
data = 30 ;
System . out. println ( "当前data:" + data) ;
System . out. println ( "当前var:" + var ) ;
}
}
Per 类:
public class Per {
String name;
static String nationality;
public Per ( ) {
}
public Per ( String name, String nationality) {
this . name = name;
this . nationality = nationality;
}
public void show ( ) {
System . out. println ( "姓名:" + name + "\t" + "国籍:" + nationality) ;
}
}
9. main方法
public class Demo08Main {
public static void main ( String [ ] args) {
int length = args. length;
System . out. println ( length) ;
if ( length > 0 ) {
for ( String arg : args) {
System . out. println ( "argument:" + arg) ;
}
}
}
}
public class Demo08UseMain {
public static void main ( String [ ] args) {
String [ ] arguments = { "1" , "2" } ;
Demo08Main . main ( arguments) ;
}
}