面向对象程序设计第一次blog
一、前言
前三次的题目集中主要是关于Java语言的基本程序设计，前两次是熟悉Java语言语法，从最基础的命名变量、选择、循环、函数、字符及字符串到第三次作业的对象和类。题目集一题量较多，但是难度不高，考察的是Java基本语法，根据以前学过的C的知识能够完成，唯一注意的是数据的精度问题以及输入输出的格式问题。题目集二难度适中，考察Java中String的使用。而题目集三虽然题量不大，但是难度却比前两次高得多，初学表示非常艰难，且很多测试点根本想不出来。
总而言之，Java是本学期首次接触的语言，存在许多问题不足，还需要多多加强训练这样才能进步
二、设计分析
1.第二次作业（7-2 串口字符解析）
代码如下：
import java.util.Scanner;
public class Main{
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
String s = in.nextLine();
int temp = 0;//记录十一位均为1
if(s.length()<11)//小于最小长度
{
System.out.println("null data");
return;
}
for(int i=0;i<11;i++)
{
if(s.charAt(i) == '1')
temp++;
}
if(temp==11)//输入数据全1，没有起始位
{
System.out.println("null data");
return;
}
if(s.matches("^[1]*$"))
{
System.out.println("null data");
return;
}
int amount = 1, num = 0,i = 0,a = 0;
boolean flag = false,index = false;
for(i=0; i<s.length()-10;i++)//判断无起始点且数据数不足
{
if(s.charAt(i)=='0')//初始位置
{
System.out.print(amount+":");
amount++;
if(s.charAt(i+10)=='0')//奇偶校验位错误
{
flag = false;
// System.out.println("parity check error");
}
else
{
num = 0;
flag = true;
for(a = i+1; a<i+9;a++)
{
if(s.charAt(a)=='1')
{
num++;
}
}
if(num%2==0)
{
if(s.charAt(i+9)=='1')
index = true;
else
index = false;
}
else
{
if(s.charAt(i+9)=='0')
index = true;
else
index = false;
}
}
if(flag==true)
{
if(index==true)
{
for(a=i+1; a<i+9;a++)
System.out.print(s.charAt(a));//输出
System.out.print("\n");
}
else
{
System.out.println("parity check error");//奇偶校验错误
}
}
else
{
System.out.println("validate error");//奇偶与结束符错误
}
i = i+10;
}
}
}
}
总结：本题对我来说难度不大，主要在于不同情况下数据读取判断，使用多组for循环来进行读取判断和输出，导致圈复杂度很高
2.第三次作业（7-1 点线形系列1-计算两点之间的距离）
代码如下：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
String s = in.nextLine();
int m = 0;//遇到逗号
int n = 0;//遇到空格
int flag = 1;//输入合法性检验
for(int i=0;i<s.length();i++) {
if(s.charAt(i)==',') {
m++;
}
if(s.charAt(i)==' ') {
n++;
}
if(s.charAt(i)=='+'||s.charAt(i)=='-'||s.charAt(i)=='.') {
if(s.charAt(i+1)>='0'&&s.charAt(i+1)<='9') {//合法输入
continue;
}
else {
flag = 0;
break;
}
}
}
if(m-n!=1) {
flag = 0;
}
if(flag == 1) {
if(m!=2) {//坐标点数量超过两个
System.out.println("wrong number of points");
}
else {
String []a = new String[4];//存放数据
for(int i = 0;i<4;i++) {
a[i] = new String();
}
int p = 0;
for(int i = 0;i<s.length();i++) {//存放 ，或空格
if(s.charAt(i)!=' '&&s.charAt(i)!=',') {
a[p] = a[p] + s.substring(i,i+1);
}
else {
p++;
}
}
int index = 1;
for(int i = 0;i<4;i++) {//判断每个数字前 + - 是否只有一个
if(a[i].charAt(0)=='+'||a[i].charAt(0)=='-') {
if(a[i].charAt(1)=='0'&&a[i].charAt(2)!='.') {
index = 0;
}
}
else {
if(a[i].length()>=2) {
if(a[i].charAt(0)=='0'&&a[i].charAt(1)!='.') {
index = 0;
}
}
}
if(index == 0) {
break;
}
}
if(index == 0) {
System.out.println("Wrong Format");
}
else{
double x1,x2,y1,y2;
x1 = Double.parseDouble(a[0]);
y1 = Double.parseDouble(a[1]);
x2 = Double.parseDouble(a[2]);
y2 = Double.parseDouble(a[3]);
double distance = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));//计算
System.out.println(distance);
}
}
}
else {
System.out.println("Wrong Format");
}
}
}
总结：这道题的题目要求很简单，就是计算两点间距离，但是它对数据输入输出的格式有很高的要求，如果输入数据不符合坐标形式，程序就要报错提醒，并且也需要格外注意坐标点数量。由于输入数据中包含空格以及逗号，我们输入时应选择字符串输入，并要对数据进行校验。在做好对输入数据的校验后，我用数组进行存放数据，最后通过距离公式来进行计算。此外，本题可以设计一个点类来完成。
3.题目三（7-2 点线形系列2-线的计算）
代码如下：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
String s = in.nextLine();
String []arry = new String[20];
String [] str= s.split(":");
int n = str.length;
int j = 0,k = 0;//数组下标
int index = 2;//坐标从第三个字符开始
int flag = 0,temp = 0;
if(n==2){
if(s.charAt(0)<=0&&s.charAt(0)>=6) {
System.out.println("Wrong Format");
return;
}
if(s.charAt(1)!=':') {
System.out.println("Wrong Format");
return;
}
for(int i=2;i<s.length();i++) {
if(s.charAt(i)==' ') {
temp++;
}
if(s.charAt(i)==','){
k++;
}
}
for(int i=2;i<s.length();i++) {//记录点
if(s.charAt(i)==','||s.charAt(i)==' ') {
arry[j] = s.substring(index,i);
index = i+1;
j++;
flag = i;
}
}
if(k == 2) {//两个点
arry[3] = s.substring(flag+1,s.length());
double x1 = Double.parseDouble(arry[0]);
double y1 = Double.parseDouble(arry[1]);
double x2 = Double.parseDouble(arry[2]);
double y2 = Double.parseDouble(arry[3]);
for(int i=0;i<s.length();i++) {
if(s.charAt(i)=='1'&&s.charAt(i+1)==':') {
Point point = new Point(x1,y1,x2,y2);
point.slope();
}
if(temp == 2) {
System.out.println("wrong number of points");
}
}
}
else if(k == 3) {//三个点
arry[5] = s.substring(flag+1,s.length());
double x1 = Double.parseDouble(arry[0]);
double y1 = Double.parseDouble(arry[1]);
double x2 = Double.parseDouble(arry[2]);
double y2 = Double.parseDouble(arry[3]);
double x3 = Double.parseDouble(arry[4]);
double y3 = Double.parseDouble(arry[5]);
if(s.charAt(0)=='2') {//选项2
Point point = new Point(x1,y1,x2,y2,x3,y3);
point.threepointdistance();
}
if(s.charAt(0)=='3') {//选项3
Point point = new Point(x1,y1,x2,y2,x3,y3);
point.threepointline();
}
if(temp == 3){
System.out.println("wrong number of points");
}
}
else if(k == 4) {//四个点
arry[7] = s.substring(flag+1,s.length());
double x1 = Double.parseDouble(arry[0]);
double y1 = Double.parseDouble(arry[1]);
double x2 = Double.parseDouble(arry[2]);
double y2 = Double.parseDouble(arry[3]);
double x3 = Double.parseDouble(arry[4]);
double y3 = Double.parseDouble(arry[5]);
double x4 = Double.parseDouble(arry[6]);
double y4 = Double.parseDouble(arry[7]);
if(s.charAt(0)=='4') {
Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4);
point.fourpointsparalle();
}
if(s.charAt(0)=='5') {
Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4);
point.jiaodian();
}
if(temp == 4) {
System.out.println("wrong number of points");
}
}
else if(k>4) {//输入点数量不符合要求
System.out.println("wrong number of points");
}
}
else{
System.out.println("Wrong Format");
}
}
}
class Point {
private double x1,y1,x2,y2,x3,y3,x4,y4;
public Point() {
super();
}
public Point(double x1,double y1,double x2,double y2) {
super();
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
}
public Point(double x1,double y1,double x2,double y2,double x3,double y3) {
super();
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.x3 = x3;
this.y3 = y3;
}
public Point(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4) {
super();
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.x3 = x3;
this.y3 = y3;
this.x4 = x4;
this.y4 = y4;
}
public double getx1() {
return x1;
}
public void setx1(double x1) {
this.x1 = x1;
}
public double gety1() {
return y1;
}
public void sety1(double y1) {
this.y1 = y1;
}
public double getx2() {
return x2;
}
public void setx2(double x2) {
this.x2 = x2;
}
public double gety2() {
return y2;
}
public void sety2(double y2) {
this.y2 = y2;
}
public double getx3() {
return x3;
}
public void setx3(double x3) {
this.x3 = x3;
}
public double gety3() {
return y3;
}
public void sety3(double y3) {
this.y3 = y3;
}
public double getx4() {
return x4;
}
public void setx4(double x4) {
this.x4 = x4;
}
public double gety4() {
return y4;
}
public void sety4(double y4) {
this.y4 = y4;
}
public boolean chonghe(double x1,double y1,double x2,double y2) {//判断两点是否重合
if(x1==x2&&y1==y2) {
return true;
}
else {
return false;
}
}
public void slope() {//斜率
double k = 0;
k = (y1-y2)/(x1-x2);
if(chonghe(x1,y1,x2,y2)) {
System.out.println("points coincide");//两点重合
}
else {
if(x1==x2) { //分母为0 线条垂直于x轴
System.out.println("Slope does not exist");
}
else {
System.out.println(k);
}
}
}
public void threepointdistance() {//第一个点与另外两条点所成线距离
double distance = Math.abs((y2-y3)*x1+(x3-x2)*y1+x2*y3-y2*x3)/Math.sqrt((y2-y3)*(y2-y3)+(x2-x3)*(x2-x3));
if(!chonghe(x2,y2,x3,y3)) {
System.out.println(distance);
}
else {
System.out.println("points coincide");
}
}
public void threepointline() {
double k1,k2;
k1 = (y1-y2)/(x1-x2);
k2 = (y1-y3)/(x1-x3);
if(!chonghe(x1,y1,x2,y2)&&!chonghe(x1,y1,x3,y3)) {
if(x1==x2&&x1==x3) {
System.out.println("true");
}
else {
if(k1==k2) {
System.out.println("true");
}
else {
System.out.println("false");
}
}
}
else {
System.out.println("points coincide");
}
}
public void fourpointsparalle() {
if(chonghe(x1,y1,x2,y2)||chonghe(x3,y3,x4,y4)) {
System.out.println("points coincide");
}
else {
if((x1-x2)*(y3-y4)==(y1-y2)*(x3-x4)) {
System.out.println("true");
}
else {
System.out.println("false");
}
}
}
public double max(double x1,double x2) {
if(x1>x2) {
return x1;
}
else {
return x2;
}
}
public double min(double x1,double x2) {
if(x1>x2) {
return x2;
}
else {
return x1;
}
}
public boolean isinline(double x,double y) {//判断交点是否在线段上
double max1 = max(x1,x2);
double max2 = max(x3,x4);
double min1 = min(x1,x2);
double min2 = min(x3,x4);
if((x>min1||x>min2)&&(x<max1||x<max2)) {
return true;
}
else {
return false;
}
}
public void jiaodian() {
double k1,k2;
double x,y;
x = (y3*x2*x4-x3*y4*x2-y3*x1*x4+y4*x1*x3-y1*x4*x2+y2*x4*x1+y1*x2*x3-y2*x1*x3)/(x4*y2-x4*y1-x3*y2+x3*y1-x2*y4+x2*y3+x1*y4-x1*y3);
y = (-y2*x4*y3+y2*x3*y4+y3*x4*y1-y4*x3*y1+y4*x2*y1-y1*x2*y3-y4*x1*y2+y2*x1*y3)/(y4*x2-y4*x1-y3*x2+x1*y3-y2*x4+y2*x3+y1*x4-y1*x3);
k1 = (y2-y1)/(x2-x1);
k2 = (y4-y3)/(x4-x3);
if(chonghe(x1,y1,x2,y2)||chonghe(x3,y3,x4,y4)) {
System.out.println("points coincide");
}
else {
if(k1==k2||(x1==x2&&x3==x4)) {
System.out.println("is parallel lines,have no intersection point");
}
else {
System.out.println(x+","+y+" "+isinline(x,y));
}
}
}
}
总结：这道题属于7-1的进阶版，由单纯点的问题转为线的问题，出现四五个点的情况，题目中需求也变得极为多，测试点也极为刁钻。这道题我设计点类来对这些需求进行计算，在此之前，还是需要对输入数据进行校验以及处理，要将输入字符拆分存放入数组，采用if判断语句来进行不同要求间算法的求解。但由于我对输入格式的判断存在问题，数据格式的输入测试点过不去，本题没有拿到满分。
SourceMonitor分析图：
4.作业3（7-3 点线形系列3-三角形的计算）
代码如下：
// package 作业第三题;
import java.util.Scanner;
import java.text.DecimalFormat;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
String s = in.nextLine();
String []arry = new String[20];
int j = 0,k = 0;//数组下标
int index = 2;//坐标从第三个字符开始
int flag = 0,temp = 0;
boolean a = false;
if(s.charAt(0)<=0&&s.charAt(0)>=6) {
System.out.print("Wrong Format");
return;
}
for(int i=0;i<s.length();i++) {
if(s.charAt(i)==' ') {
a = true;
}
}
if(s.charAt(1)!=':'||a==false) {
System.out.print("Wrong Format");
return;
}
if(!s.matches("^[1-5][:](([+-]?(0|(0\\.\\d+)|[1-9][0-9]*(\\.\\d+)?))[,]([+-]?(0|(0\\.\\d+)|[1-9][0-9]*(\\.\\d+)?))\\s?)+$")){
System.out.println("Wrong Format");
return;
}
for(int i=2;i<s.length();i++) {
if(s.charAt(i)==' ') {
temp++;
}
if(s.charAt(i)==',') {
k++;
}
}
for(int i=2;i<s.length();i++) {//记录点
if(s.charAt(i)==','||s.charAt(i)==' ') {
arry[j] = s.substring(index,i);
index = i+1;
j++;
flag = i;
}
}
if(k == 3) {//三个点
arry[5] = s.substring(flag+1,s.length());
double x1 = Double.parseDouble(arry[0]);
double y1 = Double.parseDouble(arry[1]);
double x2 = Double.parseDouble(arry[2]);
double y2 = Double.parseDouble(arry[3]);
double x3 = Double.parseDouble(arry[4]);
double y3 = Double.parseDouble(arry[5]);
if(s.charAt(0)=='1') {//选项1
Point point = new Point(x1,y1,x2,y2,x3,y3);
point.threetriangle();
}
if(s.charAt(0)=='2') {//选项2
Point point = new Point(x1,y1,x2,y2,x3,y3);
point.threepointscalculate();
}
if(s.charAt(0)=='3') {//选项3
Point point = new Point(x1,y1,x2,y2,x3,y3);
point.panduantriangle();
}
}
else if(k == 4) {//四个点
arry[7] = s.substring(flag+1,s.length());
double x1 = Double.parseDouble(arry[0]);
double y1 = Double.parseDouble(arry[1]);
double x2 = Double.parseDouble(arry[2]);
double y2 = Double.parseDouble(arry[3]);
double x3 = Double.parseDouble(arry[4]);
double y3 = Double.parseDouble(arry[5]);
double x4 = Double.parseDouble(arry[6]);
double y4 = Double.parseDouble(arry[7]);
if(s.charAt(0)=='5') {//选项五
Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4);
point.
}
}
else if(k == 5) { //五个点
arry[9] = s.substring(flag+1,s.length());
double x1 = Double.parseDouble(arry[0]);
double y1 = Double.parseDouble(arry[1]);
double x2 = Double.parseDouble(arry[2]);
double y2 = Double.parseDouble(arry[3]);
double x3 = Double.parseDouble(arry[4]);
double y3 = Double.parseDouble(arry[5]);
double x4 = Double.parseDouble(arry[6]);
double y4 = Double.parseDouble(arry[7]);
double x5 = Double.parseDouble(arry[8]);
double y5 = Double.parseDouble(arry[9]);
if(s.charAt(0)=='4') {//选项四
Point point = new Point(x1,y1,x2,y2,x3,y3,x4,y4,x5,y5);
point.fivepointstriangle();
}
}
else if(k>5) {
System.out.println("wrong number of points");
}
}
}
// package 作业第三题;
// import java.text.DecimalFormat;
class Point {
private double x1,y1,x2,y2,x3,y3,x4,y4,x5,y5;
private double x,y;
public Point() {
super();
}
public Point(double x1,double y1,double x2,double y2) {
super();
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
}
public Point(double x1,double y1,double x2,double y2,double x3,double y3) {
super();
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.x3 = x3;
this.y3 = y3;
}
public Point(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4) {
super();
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.x3 = x3;
this.y3 = y3;
this.x4 = x4;
this.y4 = y4;
}
public Point(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4,double x5,double y5) {
super();
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.x3 = x3;
this.y3 = y3;
this.x4 = x4;
this.y4 = y4;
this.x5 = x5;
this.y5 = y5;
}
public double getx1() {
return x1;
}
public void setx1(double x1) {
this.x1 = x1;
}
public double gety1() {
return y1;
}
public void sety1(double y1) {
this.y1 = y1;
}
public double getx2() {
return x2;
}
public void setx2(double x2) {
this.x2 = x2;
}
public double gety2() {
return y2;
}
public void sety2(double y2) {
this.y2 = y2;
}
public double getx3() {
return x3;
}
public void setx3(double x3) {
this.x3 = x3;
}
public double gety3() {
return y3;
}
public void sety3(double y3) {
this.y3 = y3;
}
public double getx4() {
return x4;
}
public void setx4(double x4) {
this.x4 = x4;
}
public double gety4() {
return y4;
}
public void sety4(double y4) {
this.y4 = y4;
}
public double getx5() {
return x5;
}
public void setx5(double x5) {
this.x5 = x5;
}
public double gety5() {
return y5;
}
public void sety5(double y5) {
this.y5 = y5;
}
public boolean chonghe(double x1,double y1,double x2,double y2) {//判断两点是否重合
if(x1==x2&&y1==y2) {
return true;
}
else {
return false;
}
}
public boolean triangle(double x1,double y1,double x2,double y2,double x3,double y3) {//判断是否为三角形
double a,b,c;
a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
if(a+b>c&&a+c>b&&b+c>a) {
return true;
}
else {
return false;
}
}
public void threetriangle() {
double a,b,c;
a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
if(!triangle(x1,y1,x2,y2,x3,y3)) {
System.out.println("data error");
}
else {
if(a==b||a==c||b==c) {
System.out.print("true");
}
else {
System.out.print("false");
}
System.out.print(" ");
if(a==b&&a==c&&b==c) {
System.out.print("true");
}
else {
System.out.print("false");
}
}
}
public void threepointscalculate() {
double a,b,c;
a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
double C = a+b+c;//周长
double S = Math.sqrt((C/2)*(C/2-a)*(C/2-b)*(C/2-c));//面积
double X = (x1+x2+x3)/3;
double Y = (y1+y2+y3)/3;
if(!triangle(x1,y1,x2,y2,x3,y3)) {
System.out.println("data error");
}
else {
// System.out.println(C+" "+S+" "+X+","+Y);
// System.out.printf("%.6f %.6f %.6f %.6f",C,S,X,Y);
// System.out.print(C);
// System.out.print(" ");
// System.out.print(S);
// System.out.print(" ");
// System.out.print(X);
// System.out.print(",");
// System.out.print(Y);
System.out.printf(new DecimalFormat("0.0#####").format(C));
System.out.print(" ");
System.out.printf(new DecimalFormat("0.0#####").format(S));
System.out.print(" ");
System.out.printf(new DecimalFormat("0.0#####").format(X));
System.out.print(",");
System.out.printf(new DecimalFormat("0.0#####").format(Y));
}
}
public void panduantriangle() {
double a,b,c,A,B,C;
a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
b = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
c = Math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
A = (b*b+c*c-a*a)/(2*b*c);
B = (a*a+c*c-b*b)/(2*a*c);
C = (b*b+a*a-c*c)/(2*b*a);
if(A>0&&B>0&&C>0) {
System.out.println("false false true");//锐角
return;
}
else if((Math.abs(b*b+c*c-a*a)<=0.000001)||(Math.abs(a*a+c*c-b*b)<=0.000001)||(Math.abs(b*b+a*a-c*c)<=0.000001)) {
System.out.println("false true false");//直角
return;
}
else {
System.out.println("true false false");//钝角
return;
}
}
public void jiaodian() {
double k1,k2,a1= 0,b1 = 0,c1 = 0,S1 = 0,S2 = 0,C = 0,B = 0,A = 0;
double X1,Y1,X2,Y2;
X1 = (y3*x2*x4-x3*y4*x2-y3*x1*x4+y4*x1*x3-y1*x4*x2+y2*x4*x1+y1*x2*x3-y2*x1*x3)/(x4*y2-x4*y1-x3*y2+x3*y1-x2*y4+x2*y3+x1*y4-x1*y3);
Y1 = (-y2*x4*y3+y2*x3*y4+y3*x4*y1-y4*x3*y1+y4*x2*y1-y1*x2*y3-y4*x1*y2+y2*x1*y3)/(y4*x2-y4*x1-y3*x2+x1*y3-y2*x4+y2*x3+y1*x4-y1*x3);
X2 = (y3*x2*x5-x3*y5*x2-y3*x1*x5+y5*x1*x3-y1*x5*x2+y2*x5*x1+y1*x2*x3-y2*x1*x3)/(x5*y2-x5*y1-x3*y2+x3*y1-x2*y5+x2*y3+x1*y5-x1*y3);
Y2 = (-y2*x5*y3+y2*x3*y5+y3*x5*y1-y5*x3*y1+y5*x2*y1-y1*x2*y3-y5*x1*y2+y2*x1*y3)/(y5*x2-y5*x1-y3*x2+x1*y3-y2*x5+y2*x3+y1*x5-y1*x3);
k1 = (y2-y1)/(x2-x1);
k2 = (y4-y3)/(x4-x3);
if(chonghe(x1,y1,x2,y2)||chonghe(x3,y3,x4,y4)) {
System.out.println("points coincide");
}
else {
if(k1==k2||(x1==x2&&x3==x4)) {
return;
}
else {
// System.out.println(x+","+y+" "+isinline(x,y));
a1 = Math.sqrt((x3-X1)*(x3-X1)+(y3-Y1)*(y3-Y1));
b1 = Math.sqrt((x3-X2)*(x3-X2)+(y3-Y2)*(y3-Y2));
c1 = Math.sqrt((X1-X2)*(X1-X2)+(Y1-Y2)*(Y1-Y2));
A = Math.sqrt((x4-x5)*(x4-x5)+(y4-y5)*(y4-y5));
B = Math.sqrt((x3-x5)*(x3-x5)+(y3-y5)*(y3-y5));
C = Math.sqrt((x3-x4)*(x3-x4)+(y3-y4)*(y3-y4));
S1 = 0.5 * a1 * b1 * Math.sqrt(1-((b1*b1+c1*c1-a1*a1)/2*b1*c1)*((b1*b1+c1*c1-a1*a1)/2*b1*c1));
S2 = 0.5 * B * C * Math.sqrt(1-((B*B+C*C-A*A)/2*B*C)*((B*B+C*C-A*A)/2*B*C));
if(S1<S2)
System.out.println("2 "+S1+" "+S2);
else
System.out.println("2 "+S2+" "+S1);
}
}
}
public void fivepointstriangle() {
// double a,b,c,x,y,X,Y;
boolean judge = false;
// a = Math.sqrt((x3-x4)*(x3-x4)+(y3-y4)*(y3-y4));
// b = Math.sqrt((x3-x5)*(x3-x5)+(y3-y5)*(y3-y5));
// c = Math.sqrt((x4-x5)*(x4-x5)+(y4-y5)*(y4-y5));
if(x1==x2&&y1==y2)
System.out.print("points coincide");
else {
if((x3==x4&&y3==y4)||(x3==x5&&y3==y5)||(x4==x5&&y4==y5)||(x3==x4&&x3==x5))
judge=false;
else {
if(x3==x4||x3==x5||x4==x5)
judge=true;
else {
double slope1=(y3-y4)/(x3-x4);
double slope2=(y3-y5)/(x3-x5);
if(slope1!=slope2)
judge=true;
}
}
if(judge) {
double distance1=((y1-y2)*x3+(x2-x1)*y3+x1*y2-y1*x2)/Math.sqrt((y1-y2)*(y1-y2)+(x1-x2)*(x1-x2));
double distance2=((y1-y2)*x4+(x2-x1)*y4+x1*y2-y1*x2)/Math.sqrt((y1-y2)*(y1-y2)+(x1-x2)*(x1-x2));
double distance3=((y1-y2)*x5+(x2-x1)*y5+x1*y2-y1*x2)/Math.sqrt((y1-y2)*(y1-y2)+(x1-x2)*(x1-x2));
if((distance1>0&&distance2>0&&distance3>0)||(distance1<0&&distance2<0&&distance3<0))
System.out.print("0");
else if((distance1==0&&distance2*distance3>0)||(distance2==0&&distance1*distance3>0)||(distance3==0&&distance1*distance2>0))
System.out.print("1");
else if((distance1==0&&distance2==0)||(distance1==0&&distance3==0)||(distance2==0&&distance3==0))
System.out.print("The point is on the edge of the triangle");
else {
jiaodian();
}
}
else
System.out.print("data error");
}
}
public void fourpoints(){
}
public void input(double a,double b) {
x = a;
y = b;
}
//读取x的值//
public double read_x() {
return x;
}
//读取y的值//
public double read_y() {
return y;
}
//计算两点的距离//
public double caluate_distance(Point p) {
return Math.sqrt((x-p.x )*(x-p.x )+(y-p.y )*(y-p.y));
}
//检查线的两点是否重合//
public boolean chack_point(Point p) {
boolean wssa = false ;
if(Math.abs(x-p.read_x())<1e-15&&Math.abs(y-p.read_y())<1e-15) {
wssa = true ;
}
return wssa;
}
}
class Line {
Point p1 = new Point();
Point p2 = new Point();
//检查线段的斜率是否存在//
public boolean chack_slope() {
boolean wssa = true ;
if(Math.abs(p1.read_x()-p2.read_x())<1e-15) {
wssa = false ;
}
return wssa;
}
//计算线段的斜率//
public double caluate_slope() {
return (p1.read_x()-p2.read_y())/(p1.read_x()-p2.read_y());
}
//计算点到直线的距离//
public double caluate_distance(Point a) {
double distance ;
if(if_on_line(a)){
distance = 0;
}
else {
distance = Math.abs(a.read_x()*p1.read_y()+p1.read_x()*p2.read_y()+p2.read_x()*a.read_y()-a.read_x()*p2.read_y()-p1.read_x()*a.read_y()-p2.read_x()*p1.read_y())/p1.caluate_distance(p2);
}
return distance ;
}
//判断点是否再直线上//
public boolean if_on_line(Point p) {
boolean jes = false ;
Line l1 = new Line();
Line l2 = new Line();
l1.p1 = p1;
l1.p2 = p;
l2.p1 = p2;
l2.p2 = p;
if(l1.caluate_slope()==l2.caluate_slope()) {
jes = true;
}
return jes;
}
//判断点是否在线段内//
//在线段内返回true，在线段外返回false//
public boolean if_in_line(Point p) {
boolean jes = true ;
if(p.caluate_distance(p1)>p1.caluate_distance(p2)||p.caluate_distance(p2)>p1.caluate_distance(p2)) {
jes = false ;
}
return jes;
}
//判断两直线是否平行//
//若两直线平行返回1，若两直线重合返回0，若两直线相交返回-1
public int if_parallel(Line l) {
int cnt ;
double x1 = (p1.read_x()-p2.read_x())*(l.p1.read_x()-l.p2.read_x())+(p1.read_y()-p2.read_y())*(l.p1.read_y()-l.p2.read_y());
if(x1/(p1.caluate_distance(p2)*l.p1.caluate_distance(p2))!=1) {
cnt=-1;
}
else {
if(l.caluate_distance(p1)==0) {
cnt=0;
}
else {
cnt=1;
}
}
return cnt;
}
//计算两直线交点,返回Point//
public Point caluate_intersection(Line a){
Point p = new Point();
double dx1 = p1.read_x()-p2.read_x();
double dx2 = a.p1.read_x()-a.p2.read_x();
double dy1 = p1.read_x()-p2.read_x();
double dy2 = a.p1.read_x()-a.p2.read_x();
double mid1 = dy1/dx1;
double mid2 = dy2/dx2;
double rx = (a.p2.read_y()-p2.read_y()-a.p2.read_y()*mid2+p2.read_y()*mid1)/(mid1-mid2);
double ry = (rx-p2.read_x())*mid1+p2.read_y();
p.input(rx, ry);
return p;
}
}
class Triangle {
Point p1 = new Point();
Point p2 = new Point();
Point p3 = new Point();
//检查三点是否构成三角形//
//若构成三角形返回false,若不构成三角形返回true//
public boolean chack_triangle() {
boolean err = true ;
if(Math.abs(p1.caluate_distance(p2)-p1.caluate_distance(p3))<p2.caluate_distance(p3)&&Math.abs(p1.caluate_distance(p3)+p1.caluate_distance(p2))>p2.caluate_distance(p3)){
err = false ;
}
return err ;
}
//判断是否为等边三角形，或等腰三角形//
//若为等腰三角形，返回0//
//若为等边三角形，返回1//
public int shape_line_triangle() {
int shape = 0;
if(Math.abs(p1.caluate_distance(p2)-p1.caluate_distance(p3))<1e-15&&Math.abs(p2.caluate_distance(p1)-p2.caluate_distance(p3))<1e-15) {
shape = 1;
}
return shape;
}
//计算三角形面积,返回面积//
public double caluate_S() {
return Math.abs(p1.read_x()*p2.read_y()+p2.read_x()*p3.read_y()+p3.read_x()*p1.read_y()-p1.read_x()*p3.read_y()-p2.read_x()*p1.read_y()-p3.read_x()*p2.read_y())/2;
}
//计算三角形的周长，返回周长//
public double caluate_C() {
return p1.caluate_distance(p2)+p1.caluate_distance(p3)+p2.caluate_distance(p3);
}
//计算三角形的重心坐标，返回Point//
public Point caluate_gravity_point() {
Point p = new Point();
double dx = (p1.read_x()+p2.read_x()+p3.read_x())/3;
double dy = (p1.read_y()+p2.read_y()+p3.read_y())/3;
p.input(dx, dy);
return p;
}
//判断三角形是锐角三角形还是直角三角形或钝角三角形//
//若是锐角三角形返回1，若是直角三角形返回0，若是钝角三角形则返回-1//
public int shape_horn_triangle() {
int shape ;
double j1 = (p2.read_x()-p1.read_x())*(p3.read_x()-p1.read_x())+(p2.read_y()-p1.read_y())*(p3.read_y()-p1.read_y());
double j2 = (p3.read_x()-p2.read_x())*(p1.read_x()-p2.read_x())+(p3.read_y()-p2.read_y())*(p1.read_y()-p2.read_y());
double j3 = (p1.read_x()-p3.read_x())*(p2.read_x()-p3.read_y())+(p1.read_y()-p3.read_y())*(p2.read_y()-p3.read_y());
if(j1<0||j2<0||j3<0) {
shape = 1;
}
else if(j1==0||j2==0||j3==0) {
shape = 0 ;
}
else {
shape = -1;
}
return shape;
}
//计算直线与三角形的交点//
//返回交点个数//
public int caluate_sum_intersection(Line a) {
int sum = 0;
Line l1 = new Line();
l1.p1=p1;l1.p2=p2;
Line l2 = new Line();
l2.p1=p1;l2.p2=p3;
Line l3 = new Line();
l3.p1=p2;l3.p2=p3;
if(l1.if_parallel(a)==1) {
Point point1 = a.caluate_intersection(l2);
if(l2.if_in_line(point1)) {
sum++;
}
Point point2 = a.caluate_intersection(l3);
if(l3.if_in_line(point2)) {
sum++;
}
}
else if(l2.if_parallel(a)==1) {
Point point1 = a.caluate_intersection(l1);
if(l1.if_in_line(point1)) {
sum++;
}
Point point2 = a.caluate_intersection(l3);
if(l3.if_in_line(point2)) {
sum++;
}
}
else if(l3.if_parallel(a)==1) {
Point point1 = a.caluate_intersection(l1);
if(l1.if_in_line(point1)) {
sum++;
}
Point point2 = a.caluate_intersection(l2);
if(l2.if_in_line(point2)&&point1.chack_point(point2)) {
sum++;
}
}
else {
Point point1 = a.caluate_intersection(l1);
if(l1.if_in_line(point1)) {
sum++;
}
Point point2 = a.caluate_intersection(l2);
if(l2.if_in_line(point2)&&point1.chack_point(point2)) {
sum++;
}
Point point3 = a.caluate_intersection(l2);
if(l2.if_in_line(point3)&&point1.chack_point(point3)&&point2.chack_point(point3)) {
sum++;
}
}
return sum;
}
//判断点是否再三角形内部//
public boolean if_inside(Point a) {
boolean rea = false ;
Line l1 = new Line();
l1.p1=p1;
l1.p2=a;
Line l2 = new Line();
l2.p1=p2;
l2.p2=a;
Line l3 = new Line();
l3.p1=p3;
l3.p2=a;
Line l4 = new Line();
l4.p1=p1;
l4.p2=p2;
Line l5 = new Line();
l5.p1=p2;
l5.p2=p3;
Line l6 = new Line();
l6.p1=p3;
l6.p2=p1;
if(!l5.if_in_line(l1.caluate_intersection(l5))||!l4.if_in_line(l3.caluate_intersection(l4))||!l6.if_in_line(l2.caluate_intersection(l6))) {
rea = true;
}
return rea;
}
}
总结：一开始写这道题时，想着只用点类来进行，但是在最后两个需求上，单用点类非常难实现，在前面进行字符串分割，以及前三个需求时，点类可以用的很简单，但是到了四五需求，不知道该如何设计方法，参数传递彻底搞晕，最后也尝试设计线类以及三角形类，但还是没能完成该题。
SourceMonitor分析图：
三、踩坑心得
1.这四道题我并没有全拿满分，有部分题目的部分测试点过不去，在字符串的处理上有很多地方做的不好，导致输入数据格式存在错误。
2.对类的认识还不是很充分，有很多在Main中的其实可以将其封装，导致代码冗长易出错
3.在计算上不是数学上的范围，例如判断直角三角形，应该是两边平方和减第三边平方小于一个极小值，而不是等于0，题目中就有一个测试点是关于此的，我改了很久。
4.不要怕麻烦，无论是学习正则表达式还是去多设计类，能用类的就用类，到后期会越来越方便。
四、改进建议
1.switch语句的复杂度比if语句更低，在之后的编码中能用switch替代就尽量不使用if。
2.编写代码前提前构建好类图，效率更高
3.多用类，多用方法，不要一直Main
4.String类型判断使用正则表达式很快
5.边写代码边调试，多写注释
五、总结
第一阶段的学习已经过去，我逐渐明白Java和c的相似以及不同，基本语法虽大体相同，但角度却不同了。我更熟练的运用字符串及其相关函数，并且慢慢习惯运用方法和类，但是并不熟练。对于整体的题目设计方面还需要大大加强，这样才能简化运算以及代码，可读性也会更强。另外，一定要合理规划好时间，不要拖拉，作业发布最好就快速开始，遇到问题积极寻求帮助，多想多学多问，问题总会解决的
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