JAva日常まとめ
80453 ワード
JAvaメソッドが複数の値を返すメソッド
楊輝三角
JAvaは方法で配列のコピーを実現する
クローンオブジェクト、同じアドレスと異なるアドレス
JAva instanceofの使用
マルチステートケース
JAvaダイナミックバインドメカニズムの例
マルチステート配列、バブルソート、instanceof、ダウンシフトの総合事例
練習問題、問題はコードの中にあります
package atguigu1.day08;
public class MethodTest1 {
public static void main(String[] args) {
// [ ， , 1. ，2. ]
A a = new A();
//
int[] sumAndMinus = a.getSumAndMinus(1, 4);
System.out.println(" ：" + sumAndMinus[0]);
System.out.println(" ：" + sumAndMinus[1]);
//
MyRes sumAndMinus2 = a.getSumAndMinus2(100, 12);
System.out.println(" ：" + sumAndMinus2.sum);
System.out.println(" ：" + sumAndMinus2.minus);
}
}
class A{
//
//
public int[] getSumAndMinus(int a1, int a2){
//
int arr[] = new int[2];
arr[0] = a1 + a2;
arr[1] = a1 - a2;
return arr;
}
//
public MyRes getSumAndMinus2(int a1, int a2){
MyRes myRes = new MyRes();
myRes.sum = a1 + a2;
myRes.minus = a1 - a2;
return myRes;
}
}
class MyRes{
int sum;
int minus;
}
楊輝三角
public class YangHui{
public static void main(String[] args) {
/* 5 <> <>
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1. 5
2. ， , 1 = 1 2 = 2 3 = 3
3. ， ， arr[i][j]
arr[i][j] = arr[i-1][j] + arr[i-1][j-1]; //
// -
*/
// ， ， ，
int yangHui[][] = new int[5][];
for( int i = 0; i < yangHui.length; i++) {
//i
// ，
yangHui[i] = new int[i+1];
// yangHui[i]
//
for( int j = 0; j < yangHui[i].length; j++) {
// ，1
if( j == 0 || j == yangHui[i].length - 1) {
yangHui[i][j] = 1;
} else {
yangHui[i][j] = yangHui[i-1][j] + yangHui[i-1][j-1];
}
}
}
//
for( int i = 0; i < yangHui.length; i++) {
//i
for( int j = 0; j < yangHui[i].length; j++) {
System.out.print( yangHui[i][j] + "\t");
}
System.out.println();
}
}
}
JAvaは方法で配列のコピーを実現する
package atguigu1.day08;
public class MethodTest7 {
public static void main(String[] args) {
//
MyTools myTools = new MyTools();
int arr[] = {
1,2,3,4,5};
int[] arrNew = myTools.copyArray(arr,2);
// arr arrNew
myTools.printArr(arr);
myTools.printArr(arrNew);
}
}
class MyTools{
//
public void printArr(int arr[]){
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + "\t");
}
System.out.println();
}
public int[] copyArray(int[] arr, int count){
//
count = count > arr.length ? arr.length : count;
//System.out.println(count);
//
int arrNew[] = new int[count];
//
for (int i = 0; i < count; i++) {
arrNew[i] = arr[i];
}
return arrNew;
}
}
クローンオブジェクト、同じアドレスと異なるアドレス
package atguigu1.day08;
public class MethodTest9 {
public static void main(String[] args) {
/*
3) copyPerson， Person ， 。 。。，
，
//
1. copyPerson
2. Person
Person
*/
S s = new S();
//
Person p = new Person();
p.name = " ";
p.age = 421;
Person p1 = p ;//p p1 s.copyPerson(p); //p p1
System.out.println("p1.anme=" + p1.name + " p1.age=" + p1.age);
}
}
class S{
public Person copyPerson(Person p){
// Person
Person person = new Person();
// person
person.name = p.name;
person.age = p.age;
return person;
}
}
class Person{
public String name;
public int age;
}
JAva instanceofの使用
package com.atguigu.day12;
/*
* instanceOf ， XX XX 【 】
*/
public class InstanceOfDemo {
public static void main(String[] args) {
Object obj1 = new Object();
String str1 = new String("Hello");
Taiger taiger = new Taiger();
// obj1 object object
System.out.println(obj1 instanceof Object); //true
System.out.println(str1 instanceof Object); //true
System.out.println(taiger instanceof Object); //true
System.out.println(taiger instanceof Monster); //true
System.out.println(obj1 instanceof Taiger); //false
}
}
class Taiger extends Monster{
}
class Monster{
}
マルチステートケース
package com.atguigu.day12;
public class TestFiledMethod {
public static void main(String[] args) {
Sub2 sub = new Sub2();
System.out.println(sub.count); //20
sub.display(); //20
/*
* ：
* ： ，
* ： ，
*/
Base2 s = sub; //s
System.out.println(s.count); //10
s.display(); //20
}
}
class Base2{
int count =10;
public void display(){
System.out.println(this.count);
}
}
class Sub2 extends Base2{
int count = 20;
public void display(){
System.out.println(this.count);
}
}
JAvaダイナミックバインドメカニズムの例
package com.atguigu.day12;
public class PolyExam03 {
public static void main(String[] args) {
AAA a = new BBB(); //
System.out.println(a.sum()); //40
System.out.println(a.sum1()); //30
System.out.println(" ");
System.out.println(a.sum());
// 30 getI BBB ， ， ，
System.out.println(a.sum1());
//20 I i
}
}
/*
* java
* ， （ ）
* ， ， 。
*/
class AAA {
public int i = 10;
public int sum() {
return getI() + 10;
}
public int sum1() {
return i + 10;
}
public int getI() {
return i;
}
}
class BBB extends AAA {
public int i = 20;
// public int sum() {//
// return i + 20;
// }
public int getI() {
return i;
}
// public int sum1() {// ?
// return i + 10;
// }
}
マルチステート配列、バブルソート、instanceof、ダウンシフトの総合事例
package com.atguigu.day12;
/*
*
*/
public class PolyArr {
public static void main(String[] args) {
Person person[] = new Person[5];
// ,
person[0] = new Person("jack", 30);
person[1] = new Student("smith", 26);
person[2] = new Student("tom", 20);
person[3] = new Teacher("joker", 40);
person[4] = new Teacher("king", 39);
for (int i = 0; i < person.length; i++) {
System.out.println(person[i]);
}
//
Person temp = null; //
for (int i = 0; i < person.length - 1; i++) {
for (int j = 0; j < person.length - 1 - i; j++) {
// ，
if (person[j].getAge() > person[j + 1].getAge()) {
temp = person[j];
person[j] = person[j + 1];
person[j + 1] = temp;
}
}
}
//
System.out.println("========================");
for (int i = 0; i < person.length; i++) {
System.out.println(person[i]);
}
// persons ， study teach
// instanceof ..
System.out.println("######################");
for (int i = 0; i < person.length; i++) {
if(person[i] instanceof Student){
// ， ，
//
//
((Student)person[i]).study();
}else if(person[i] instanceof Teacher){
//
//
Teacher tea = (Teacher)person[i];
tea.teach();
}else
System.out.println("Person ");
}
}
}
/*
* ( ): ： Person、Student [2] Teacher[2] ，
* ( )， say name age， .
*/
class Person {
private String name;
private int age;
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + "]";
}
}
class Student extends Person {
public Student(String name, int age) {
super(name, age);
// TODO Auto-generated constructor stub
}
public void study() {
System.out.println(" " + getName() + " ....");
}
}
class Teacher extends Person {
public Teacher(String name, int age) {
super(name, age);
// TODO Auto-generated constructor stub
}
public void teach() {
System.out.println(" " + getName() + " ....");
}
}
練習問題、問題はコードの中にあります
package com.atguigu.day12;
public class PolyParameter {
public static void main(String[] args) {
Worker3 worker3 = new Worker3(" ", 200, 8);
PolyParameter polyParameter = new PolyParameter();
polyParameter.showEmpAnnal(worker3); // 1600.0
Manager3 manager3 = new Manager3(" ", 250, 10, 6000);
polyParameter.showEmpAnnal(manager3);
// ~
// 8500.0
polyParameter.testWork(worker3);// ..
polyParameter.testWork(manager3);// ....
}
// showEmpAnnal(Employee e)，
// , main
// ， ， ， ，
//
public void showEmpAnnal(Employee3 e) {
System.out.println(e.getName() + " " + e.getAnnual());
}
// ，testWork, ，
// work ， ， manage
// 【 + instanceof + 】
public void testWork(Employee3 e) {
// ， ，
if(e instanceof Worker3) {
//
((Worker3)e).work();
} else if(e instanceof Manager3) {
//
((Manager3)e).manage();
} else {
System.out.println(" ");
}
}
}
/*
* 2: • Employee3， [private]，
* getAnnual 。 (Worker3) (Manager3) ，
* bonus manage ， work ， getAnnual
*
*
*/
class Employee3 {
private String name;
private double monSal; //
private int salMon; //
public Employee3(String name, double monSal, int salMon) {
super();
this.name = name;
this.monSal = monSal;
this.salMon = salMon;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getMonSal() {
return monSal;
}
public void setMonSal(double monSal) {
this.monSal = monSal;
}
public int getSalMon() {
return salMon;
}
public void setSalMon(int salMon) {
this.salMon = salMon;
}
public double getAnnual() {
return monSal * salMon;
}
}
class Worker3 extends Employee3 {
public Worker3(String name, double monSal, int salMon) {
super(name, monSal, salMon);
// TODO Auto-generated constructor stub
}
//
public void work() {
System.out.println(" " + getName() + " ..");
}
// getAnnual
@Override
public double getAnnual() {
// TODO Auto-generated method stub
return super.getAnnual();
}
}
class Manager3 extends Employee3 {
private double bonus; //
public Manager3(String name, double monSal, int salMon, double bonus) {
super(name, monSal, salMon);
this.bonus = bonus;
}
public double getBonus() {
return bonus;
}
public void setBonus(double bonus) {
this.bonus = bonus;
}
//
public void manage() {
System.out.println(" " + getName() + " ....");
}
// getAnnual
@Override
public double getAnnual() {
// ， bonus ，
System.out.println(" ~");
return super.getAnnual() + bonus;
}
}