java面向对象练习6方法形参的值传递机制测试

/*

• 变量的赋值
• 变量是基本数据类型时&＃xff1a;此时赋值的是变量所保存的数据值
• 变量是引用数据类型时&＃xff1a;此时赋值的是变量所保存的数据的地址值
• 方法中参数的传递机制
• 方法必须由其所在类或对象调用才有意义。若方法含有参数&＃xff1a;
• 实参&＃xff1a;方法调用时实际传递给形参的参数值
• 形参&＃xff1a;方法声明时的参数
• Java中方法的参数传递方式只有一种&＃xff1a;值传递。将实际参数值的副本传入方法内&＃xff0c;而参数本身不受影响。
• 形参是基本数据类型时&＃xff1a;将实参的基本数据类型的数据值传递给形参
• 形参是引用数据类型时&＃xff1a;将实参的引用数据类型变量的地址值传递给形参

*/

package com.atguigu.contact;
import java.util.*;
public class Object6 {public static void main(String[] args) {Scanner scan &＃61; new Scanner(System.in);//变量赋值情况int a &＃61; 23;int b &＃61; a;b &＃61; 11;System.out.println("a&＃61;" &＃43; a &＃43; ",b&＃61;" &＃43; b);Arguments argu &＃61; new Arguments();argu.num &＃61; 33;Arguments argu1 &＃61; argu;System.out.println(argu.num &＃43; " " &＃43; argu1.num);argu1.num &＃61; 22;System.out.println(argu.num &＃43; " " &＃43; argu1.num);//方法形参传递测试1//交换方法形参为基本数据类型&＃xff0c;变量m&＃xff0c;n与方法形参m&＃xff0c;n都在栈空间中存储&＃xff0c;指向两套地址。int m &＃61; 11;int n &＃61; 22;System.out.println("m &＃61; " &＃43; m &＃43; ",n &＃61; " &＃43; n);//m &＃61; 11,n &＃61; 22argu.exchange(m, n);System.out.println("m &＃61; " &＃43; m &＃43; ",n &＃61; " &＃43; n);//m &＃61; 11,n &＃61; 22,交换失败//交换方法形参为引用基本数据类型&＃xff0c;变量d与方法中date指向同一地址值&＃xff0c;操作同一块堆空间。Date d &＃61; new Date();d.m &＃61; 11;d.n &＃61; 22;System.out.println("m &＃61; " &＃43; d.m &＃43; ",n &＃61; " &＃43; d.n);//m &＃61; 11,n &＃61; 22argu.swap(d);System.out.println("m &＃61; " &＃43; d.m &＃43; ",n &＃61; " &＃43; d.n);//m &＃61; 22,n &＃61; 11,交换成功Date d1 &＃61; new Date();d1.m &＃61; 11;d1.n &＃61; 22;System.out.println("m &＃61; " &＃43; d1.m &＃43; ",n &＃61; " &＃43; d1.n);//m &＃61; 11,n &＃61; 22argu.swap1(d1);System.out.println("m &＃61; " &＃43; d1.m &＃43; ",n &＃61; " &＃43; d1.n);//m &＃61; 11,n &＃61; 22,交换失败//方法形参传递测试2Object6 o &＃61; new Object6();o.frist();//0, 9//17, 7//遍历数组每个元素除以第一个元素形成新数组//说明&＃xff1a;数组元素在运算后会被改变赋值&＃xff0c;需要创建临时变量储存首元素值&＃xff0c;或者倒序遍历int[] arr &＃61; new int[] {11,23,45,6,78,7,90,12,11};System.out.println(Arrays.toString(arr));//错误方式for (int i &＃61; 0; i < arr.length; i&＃43;&＃43;) {arr[i] &＃61; arr[i] / arr[0];}System.out.println(Arrays.toString(arr));//正确方式1int[] arr1 &＃61; new int[] {11,23,45,6,78,7,90,12,11};for (int i &＃61; arr1.length - 1; i >&＃61; 0; i--) {arr1[i] &＃61; arr1[i] / arr1[0];}System.out.println(Arrays.toString(arr1));//正确方式2int[] arr2 &＃61; new int[] {11,23,45,6,78,7,90,12,11};int temp &＃61; arr2[0];for (int i &＃61; 0; i < arr2.length; i&＃43;&＃43;) {arr2[i] &＃61; arr2[i] / temp;}System.out.println(Arrays.toString(arr2));//测试题3&＃xff0c;println方法的特例int[] array &＃61; new int[] {1,2,3};System.out.println(array);//输出地址值char[] array1 &＃61; new char[] {&＃39;a&＃39;,&＃39;b&＃39;,&＃39;c&＃39;};System.out.println(array1);//输出abc//测试题4&＃xff0c;输出圆的面积CircleA c &＃61; new CircleA();c.radius &＃61; 4.5;System.out.println(c.findArea());ErgodicCircleA circle &＃61; new ErgodicCircleA();circle.printAreas(c, 10);//circle.printAreas(new CircleA(),10);只调用一次Circle类&＃xff0c;可以使用匿名对象的形式//测试题5&＃xff0c;无关方法值传递int i &＃61; 10;int j &＃61; 20;method(i,j);//编写方法method&＃xff0c;实现输出 i &＃61; 100&＃xff0c;j &＃61; 200System.out.println("i &＃61; " &＃43; i);System.out.println("j &＃61; " &＃43; j);}public static void method(int i,int j) {i &＃61; i * 10;j &＃61; j * 10;System.out.println("i &＃61; " &＃43; i);System.out.println("j &＃61; " &＃43; j);System.exit(0);//退出JVM&＃xff0c;不在输出后面的语句}//方法二&＃xff0c;方法重写&＃xff0c;调用新的println方法&＃xff0c;输出特定结果
// public static void method1(int i,int j) {
// PrintStream ps &＃61; new PrinStream(System.out)
// {
// public void printlin(String x) {
// if("i &＃61; 10".equals(x)) {
// x &＃61; "i &＃61; 100";
// }else if("j &＃61; 20".equals(x)) {
// x &＃61; "j &＃61; 200";
// }
// super.println(x);
//
// }
// };
// System.setOut(ps);
// }//Object6 类内创建方法frist&＃xff0c;second以供测试2调用public void frist() {int m &＃61; 7;Date d &＃61; new Date();d.m &＃61; 11;second(d,m);System.out.println(d.m &＃43; ", " &＃43; m);}public void second(Date d,int m) {m &＃61; 9;d.m &＃61; 17;Date da &＃61; new Date();d &＃61; da;System.out.println(d.m &＃43; ", " &＃43; m);}}
//为测试一创建类Arguments
class Arguments{int num;public int setValue(int i) {return i;}public void exchange(int m,int n) {//方法内参数为基本数据类型&＃xff0c;接收实参数据值&＃xff0c;交换方法内变量m&＃xff0c;n&＃xff0c;与方法外变量m&＃xff0c;n无关int temp;temp &＃61; m;m &＃61; n;n &＃61; temp;}public void swap(Date date) {//参数是引用数据类型时交换地址值&＃xff0c;这样才能对方法外的变量实现交换int temp;temp &＃61; date.m;date.m &＃61; date.n;date.n &＃61; temp;}public void swap1(Date date) {date &＃61; new Date();//相当于在堆中新建一个空间&＃xff0c;date指向新地址值&＃xff0c;后面语句不影响dint temp;temp &＃61; date.m;date.m &＃61; date.n;date.n &＃61; temp;}}
//创建类Date为测试2使用
class Date{int m ;int n ;
}
//创建类CircleA为测试4使用
class CircleA{double radius;public double findArea() {return radius * radius * Math.PI;}
}
//创建类ErgodicCircle为测试4使用
class ErgodicCircleA{public void printAreas(CircleA c,int i) {System.out.println("Radius\t\tArea");for (int j &＃61; 1; j <&＃61; i; j&＃43;&＃43;) {c.radius &＃61; j;System.out.println(c.radius &＃43; "\t\t" &＃43; c.findArea());}}
}