Java學習第二十三天＜物件分配機制＞＜方法＞＜成員方法傳參機制＞
阿新 • • 發佈：2022-03-11
物件分配機制
package chapter06.D1物件分配機制;
public class Object01 {
public static void main(String[] args) {
Person p1 = new Person();
p1.age=10;
p1.name="小明";
Person p2=p1;//p1賦給了p2 或讓p2指向p1 共享物件空間地址
p1.age=80;
System.out.println(p2.age);
}
}
class Person{
String name;
int age;
}
package chapter06.D1物件分配機制;
public class Object02 {
public static void main(String[] args) {
Person a=new Person();
a.age=10;
a.name="小明";
Person b;
b=a;
System.out.println(b.name);//小明
b.age=200;
b=null;
System.out.println(a.age);//200
System.out.println(b.age);//異常
}
}
方法
package chapter06.D2方法;
public class Method01 {
public static void main(String[] args) {
Person p1 = new Person();
p1.cal01();
p1.cal02(200);
System.out.println(p1.getSum(52,58));
}
}
class Person{
public void cal01(){
int res=0;
for (int i = 1; i <=1000; i++) {
res+=i;
}
System.out.println("cal01計算結果"+res);
}
public void cal02(int n){//可傳參
int res=0;
for (int i = 1; i <=n; i++) {//n可賦值
res+=i;
}
System.out.println("cal02計算結果"+res);
}
public int getSum(int num1,int num2){
int res=num1+num2;
return res;
}
}
package chapter06.D2方法;
//返回多個引數
public class MethodDetail {
public static void main(String[] args) {
AA a = new AA();
int [] res=a.getSumAndSub(1,4);
System.out.println("和="+res[0]);
System.out.println("差="+res[1]);
}
static class AA{
public int[] getSumAndSub(int n1,int n2){
int[]resArr=new int[2];
resArr[0]=n1+n2;
resArr[1]=n1-n2;
return resArr;
}
}
}
package chapter06.D2方法;
public class MethodDetail02 {
public static void main(String[] args) {
A a = new A();
a.sayok();
a.m1();
}
}
//同一個類的方法呼叫：直接呼叫即可
class A{
public void print(int n){
System.out.println("print()方法被呼叫 n="+n);
}
public void sayok(){
print(10);
System.out.println("繼續執行say ok");
}
public void m1(){
B b = new B();
b.hi();//跨A類呼叫B類方法，要通過物件名呼叫
}
}
class B {
public void hi(){
System.out.println("B類中的hi（）被執行");
}
}
package chapter06.D2方法;
public class MethodExercise {
public static void main(String[] args) {
AA a = new AA();
if (a.isOdd(1)){
System.out.println("是奇數");
}else {
System.out.println("是偶數");
}
a.print(4,4,'#');
}
}
class AA{
public boolean isOdd(int num){
/*
if (num%2!=0){
return true;
}else {
return false;
}*/
return num%2!=0?true:false;
}
public void print(int row,int col,char c){
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
System.out.print(c);
}
System.out.println();
}
}
}
成員方法傳參機制
package chapter06.D3成員方法傳參機制;
public class MethodParameter {
public static void main(String[] args) {
int a=10;
int b=20;
AA aa = new AA();
aa.swap(a,b);
System.out.println();
System.out.println("a="+a+"b="+b);//主方法裡的變數
}
}
class AA{
public void swap(int a,int b){
System.out.printf("交換前 a="+a+"\tb="+b);
int temp=a;
a=b;
b=temp;//交換
System.out.println();
System.out.printf("交換後 a="+a+"\tb="+b);
}
}
package chapter06.D3成員方法傳參機制;
public class MethodParameter02 {
public static void main(String[] args) {
B b = new B();
int []arr={1,2,3};
b.test100(arr);
System.out.println("main的arr陣列");
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]+"\t");
}
System.out.println();
Person p = new Person();
p.name="jack";
p.age=10;
b.test200(p);
System.out.println("main的p.age="+p.age);
}
}
class Person{
String name;
int age;
}
class B{
public void test200(Person p){
p.age=10000;
}
public void test100(int[] arr){
arr[0]=200;
//遍歷陣列
System.out.println("test100的arr陣列");
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]+"\t");
}
System.out.println();
}
}