//exercise 3.1package thirdchapterexercise1;import java.util.Scanner;public class first {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in =new Scanner(System.in);        System.out.print("Enter a,b,c:");        double a=in.nextDouble();        double b=in.nextDouble();        double c=in.nextDouble();        double judge=b*b-4*a*c;        if (judge>0){            double x1=(-b+(Math.pow(judge, 0.5)))/(2*a);            double x2=(-b-(Math.pow(judge, 0.5)))/(2*a);            System.out.println("The roots are "+x1+" and "+x2);        }        else if (judge==0){            double x=(-b)/(2*a);            System.out.println("The root is "+x);        }        else             System.out.println("The equation has no real roots");    }}//exercise 3.2package thirdchapterexercise1;import java.util.Scanner;public class second {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in =new Scanner(System.in);        System.out.print("Enter an integer:");        int integer=in.nextInt();        System.out.println("Is "+integer+" an even number?"+(integer%2==0));    }}//exercise 3.3package thirdchapterexercise1;import java.util.Scanner;public class third {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("Enter a,b,c,d,e,f:");        double a=in.nextDouble(),b=in.nextDouble(),c=in.nextDouble(),d=in.nextDouble();        double e=in.nextDouble(),f=in.nextDouble();        double judge=a*d-b*c;        if (judge==0){            System.out.println("The equation has no solution");            System.exit(0);        }        double x=(e*d-b*f)/judge;        double y=(a*f-e*c)/judge;        System.out.println("x is "+x+" and y is "+y);    }}//exercise 3.4package thirdchapterexercise1;import java.util.Scanner;public class fourth {    public static void main(String[] args) {        // TODO Auto-generated method stub        int number1=(int)(Math.random()*100);        int number2=(int)(Math.random()*100);        Scanner in=new Scanner(System.in);        System.out.print("What is "+number1+" + "+number2+"?");        int input=in.nextInt();        System.out.println("Your answer is "+(number1+number2==input));    }}//exercise 3.5package thirdchapterexercise1;import java.util.Scanner;public class fifth {    public static void main(String[] args) {        // TODO Auto-generated method stub        int number1=(int)(Math.random()*10);        int number2=(int)(Math.random()*10);        int number3=(int)(Math.random()*10);                Scanner in=new Scanner(System.in);        System.out.print("What is "+number1+" + "+number2+" + "+number3+"?");        int input =in.nextInt();                System.out.println("Your answer is "+(number1+number2+number3==input));            }}//exercise 3.6package thirdchapterexercise1;import java.util.Scanner;public class sixth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);                //input pounds        System.out.print("Enter weight in pounds:");        double weight=in.nextDouble();                //input feet        System.out.print("Enter feet:");        int feet =in.nextInt();                        //input inches        System.out.print("Enter height in inches:");        int height =in.nextInt();                //The feet and inches to meter,The pounds into kilograms        double kilograms=weight*0.45359237;        double meter=height*0.0254+feet*0.3048;                //get BMI        double bmi=kilograms/Math.pow(meter, 2);                System.out.println("Your BMI is "+bmi);                //The weight classification        if(bmi<16)            System.out.println("You are seriously underweight");        else if (bmi<18)            System.out.println("You are underweight");        else if (bmi<24)            System.out.println("You are normal weight");        else if (bmi<29)            System.out.println("Yo are overweight");        else if (bmi<35)            System.out.println("You are seriously overweight");        else             System.out.println("You are gravely overweight");    }}//exercise 3.8package thirdchapterexercise1;import javax.swing.JOptionPane;public class seventh {    public static void main(String[] args) {        // TODO Auto-generated method stub        String number1=JOptionPane.showInputDialog("input number1:");        String number2=JOptionPane.showInputDialog("input number1:");        String number3=JOptionPane.showInputDialog("input number1:");        int num1=Integer.parseInt(number1);        int num2=Integer.parseInt(number2);        int num3=Integer.parseInt(number3);        int temp;        if (num1>num2){            temp=num1;            num1=num2;            num2=temp;        }        if(num2>num3){            temp=num2;            num2=num3;            num3=temp;        }        if(num1>num2){            temp=num1;            num1=num2;            num2=temp;        }        System.out.println(num1+"\t"+num2+"\t"+num3);    }}//exercise 3.9package thirdchapterexercise1;import java.util.Scanner;public class eighth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);                System.out.print("input number:");        String number=in.next();                //字符串转化为字符数组        char a[]=number.toCharArray();                        int b[]=new int[number.length()],sum=0;        for(int i =0;i<number.length();i++){                        //将字符数组转化为数字数组            b[i]=((int)a[i]-48)*(i+1);                        //sum            sum=sum+b[i];        }        int d10=sum%11;                //将数字转化为字符，        char d=(char)(d10+48);                //连接字符串        number=number+d;                System.out.println("ISBN is "+number);    }}//exercise 3.10package thirdchapterexercise1;import java.util.Scanner;public class ninth {    public static void main(String[] args){        int number1=(int)(Math.random()*10);        int number2=(int)(Math.random()*10);                if(number1<number2){            int temp=number1;            number1=number2;            number2=temp;        }                System.out.print("What is "+number1+"+"+number2+"? ");        Scanner in=new Scanner(System.in);        int answer=in.nextInt();                if(number1+number2==answer)            System.out.println("You are correct!");        else            System.out.println("Your answer is wrong\n"+number1+"+"+number2+" sho"                    + "uld be "+(number1+number2));            }}//exercise 3.11package thirdchapterexercise1;import java.util.Scanner;public class tenth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("please input mouth and year:");        int mouth=in.nextInt();        int year=in.nextInt();        switch(mouth){        case 1:            System.out.println("January "+year+" has 31 days");            break;        case 3:            System.out.println("March "+year+" has 31 days");            break;        case 4:            System.out.println("April"+year+" has 30 days");            break;        case 5:            System.out.println("May "+year+" has 31 days");            break;        case 6:            System.out.println("June "+year+" has 30 days");            break;        case 7:            System.out.println("July "+year+" has 31 days");            break;        case 8:            System.out.println("August "+year+" has 31 days");            break;        case 9:            System.out.println("September "+year+" has 30 days");            break;        case 10:            System.out.println("October "+year+" has 31 days");            break;        case 11:            System.out.println("November "+year+" has 30 days");            break;        case 12:            System.out.println("December "+year+" has 31 days");            break;        default:            break;        }        if(mouth==2){            if(year%4==0&&year%100!=0||year%400==0){                System.out.println("February "+year+" has 29 days");                }            else            {                System.out.println("February "+year+" has 20 days");                            }            }    }}

//exercise 3.12package thirdchapterexercise2;import java.util.Scanner;public class first {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);                System.out.print("please input a integer:");        int input=in.nextInt();                if(input%5==0&&input%6==0)            System.out.println(input+" is divisible by both 5 and 6");        else if (input %5==0^input%6==0)            System.out.println(input+" is dibisible by 5 or 6,but not both");        else             System.out.println(input+" is not divisible by either 5 or 6");    }}//exercise 3.14package thirdchapterexercise2;import java.util.Scanner;public class second {    public static void main(String[] args) {        // TODO Auto-generated method stub        int random=(int)(Math.random()*100)%2;        String computer;                //指定random        if (random==0){            computer="tails";        }        else            computer="heads";                    Scanner in=new Scanner(System.in);        System.out.println("(please input heads of tails)");        String input =in.next();        if((random==1&&input.equals("heads"))||(random==0&&input.equals("tails"))){            System.out.println("computer is "+computer);            System.out.println("You are right!");        }        else {            System.out.println("computer is "+computer);            System.out.println("You are wrong!");        }    }}//exercise 3.15package thirdchapterexercise2;import java.util.Scanner;public class third {    public static void main(String[] args) {        // lottery number        int lottery=(int)(Math.random()*1000);                Scanner in=new Scanner(System.in);                System.out.print("Enter your lottery pick (three digits):");        int guess =in.nextInt();                //separation lottery digit        int lotteryDigit1=lottery/100;        int lotteryDigit2=lottery/10%10;        int lotteryDigit3=lottery%10;                //separation guess digit        int guessDigit1=guess/100;        int guessDigit2=guess/10%10;        int guessDigit3=guess%10;                System.out.println("The lottery number is "+lottery);                //judge        if (guess == lottery)            System.out.println("Exact match:you win $10000");        else if((guessDigit2==lotteryDigit1                ||guessDigit2==lotteryDigit3)                &&(guessDigit1==lotteryDigit2                ||guessDigit1==lotteryDigit3)                &&(guessDigit3==lotteryDigit1                ||guessDigit3==lotteryDigit2))            System.out.println("Match all digits: you win $3000");        else if(guessDigit1==lotteryDigit1                ||guessDigit1==lotteryDigit2                ||guessDigit1==lotteryDigit3                ||guessDigit2==lotteryDigit1                ||guessDigit2==lotteryDigit2                ||guessDigit2==lotteryDigit3                ||guessDigit3==lotteryDigit1                ||guessDigit3==lotteryDigit2                ||guessDigit3==lotteryDigit3)            System.out.println("Match one digit:you win $ 1000");        else            System.out.println("Sorry,no match");    }}//exercise 3.16package thirdchapterexercise2;public class fourth {    public static void main(String[] args) {        // TODO Auto-generated method stub        int a=(int)(Math.random()*26)+‘A‘;        char b=(char)a;        System.out.println(b);            }}//exercise 3.17package thirdchapterexercise2;import java.util.Scanner;public class fifth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("scissor(0),rock(1),paper(2):");        int input=in.nextInt();        int computer=(int)(Math.random()*3);        if(computer==0&&input==1)            System.out.print("The computer is scissor.You are rock.You win");        else if (computer==0&&input==2)            System.out.print("The computer is scissor.You are paper.You 输了.");        else if (computer==0&&input==0)            System.out.print("The computer is scissor.You are scissor.It is a draw.");                else if (computer==1&&input==0)            System.out.print("The computer is rock.You are scissor.You 输了.");        else if (computer==1&&input==1)            System.out.print("The computer is rock.You are rock.It is a draw.");        else if (computer==1&&input==2)            System.out.print("The computer is rock.You are paper.You win.");                else if (computer==2&&input==0)            System.out.print("The computer is paper.You are scissor.You win.");        else if (computer==2&&input==1)            System.out.print("The computer is paper.You are rock.You 输了.");        else if (computer==2&&input==2)            System.out.print("The computer is paper.You are paper.It is a draw.");            }}//exercise 3.18package thirdchapterexercise2;import javax.swing.JOptionPane;public class sixth {    public static void main(String[] args) {        // TODO Auto-generated method stub        String year=JOptionPane.showInputDialog("Enter a year:");        int year1=Integer.parseInt(year);        boolean isLeapYear=(year1%4==0&&year1%100!=0)||(year1%400==0);        JOptionPane.showMessageDialog(null,year1+"is a leap year?"+isLeapYear);    }}//exercise 3.19package thirdchapterexercise2;import java.util.Scanner;public class seventh {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("Enter three edges:");        double side1=in.nextDouble();        double side2=in.nextDouble();        double side3=in.nextDouble();        double max=side1,sum=0;                if(max<side2){            max=side2;            sum=sum+side1;        }        else             sum=sum+side2;                if(max<side3){            max=side3;            sum=sum+side2;        }        else             sum=sum+side3;                System.out.println("Can edges "+side1+","+side2+" and "+side3+" form a "                + "triangle?"+(sum>max));            }}//exercise 3.20package thirdchapterexercise2;import java.util.Scanner;public class eighth {    public static void main(String[] args) {        // TODO Auto-generated method stubScanner in=new Scanner(System.in);                System.out.println("please input -58F to 41F of temperature and better than 2 of "                + "wind speed!!");                //input Fahrenheit        System.out.print("Enter the temperature in Fahrenheit:");        double fahreheit=in.nextDouble();        if(fahreheit<-58||fahreheit>41){            System.out.println("input error!!");            System.exit(0);        }        //input wind speed        System.out.print("Enter the wind speed miles per hours:");        double windspeed=in.nextDouble();        if (windspeed<2){            System.out.println("input error!!");            System.exit(0);        }                double windchillindex=35.74+0.6215*fahreheit-35.75*Math.pow(windspeed,0.16)+                0.4275*fahreheit*Math.pow(windspeed,0.16);        System.out.print("The wind chill index is "+windchillindex);    }}//exercise 3.21package thirdchapterexercise2;import java.util.Scanner;public class ninth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("Enter year:(e.g.m 2008):");        int year=in.nextInt();        System.out.print("Enter month : 1-12:");        int month=in.nextInt();        System.out.print("Enter the day of the month: 1-31:");        int day=in.nextInt();                if (month==1||month==2){            month=month+12;            year--;        }                int q=(day+(26*(month+1)/10)+year%100+year%100/4+year/100/4+5*year/100)%7;                switch(q){        case 0:            System.out.println("Day of the weel is Saterday");            break;        case 1:            System.out.println("Day of the weel is Sunday");            break;        case 2:            System.out.println("Day of the weel is Monday");            break;        case 3:            System.out.println("Day of the weel is Tuesday");            break;        case 4:            System.out.println("Day of the weel is Wednesday");            break;        case 5:            System.out.println("Day of the weel is Thursday");            break;        case 6:            System.out.println("Day of the weel is Friday");            break;        }    }}//exercise 3.22package thirdchapterexercise2;import java.util.Scanner;public class tenth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("Enter a point with two coordinates:");        double x=in.nextDouble();        double y=in.nextDouble();        double distance=Math.pow((x*x+y*y),0.5);                if (distance<10){            System.out.print("Point("+x+","+y+") is in the circle ");        }        else             System.out.print("Point("+x+","+y+") is not in the circle ");    }}//exercise 3.23package thirdchapterexercise3;import java.util.Scanner;public class first {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("Enter a point with two coordinates:");        double x=in.nextDouble();        double y=in.nextDouble();                //horizontal is x        double horizontal=x;                //vertical is y        double vertical=y;                if (horizontal<5&&vertical<2.5)            System.out.print("Point("+x+","+y+") is in the rectangle");        else             System.out.print("Point("+x+","+y+") is not in the rectangle");    }}//exercise 3.24package thirdchapterexercise3;public class second {    public static void main(String[] args) {        // TODO Auto-generated method stub        int number1=(int)(Math.random()*13);        int color1=(int)(Math.random()*4);        String number=null,color=null;        switch(number1){        case 0:            number="Ace";            break;        case 1:            number="2";            break;        case 2:            number="3";            break;        case 3:            number="4";            break;        case 4:            number="5";            break;        case 5:            number="6";            break;        case 6:            number="7";            break;        case 7:            number="8";            break;        case 8:            number="9";            break;        case 9:            number="10";            break;        case 10:            number="Jack";            break;        case 11:            number="Queen";            break;        case 12:            number="King";            break;        default:            break;        }        switch(color1){        case 0:            color="Clubs";            break;        case 1:            color="Diamond";            break;        case 2:            color="Heart";            break;        case 3:            color="Spades";            break;        }        System.out.println("The card you picked is "+number+" of "+color);    }}//exercise 3.25package thirdchapterexercise3;import java.util.Scanner;public class third {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("Enter three edges:");        double side1=in.nextDouble();        double side2=in.nextDouble();        double side3=in.nextDouble();        double max=side1,sum=0;                //find max and sum of two side        //Judge whether existence of triangle        if(max<side2){            max=side2;            sum=sum+side1;        }        else             sum=sum+side2;                if(max<side3){            max=side3;            sum=sum+side2;        }        else             sum=sum+side3;                //calculate the perimeter        double perimeter=sum+max;        if(sum<max||sum==max)            System.out.println("input is wrong");        else            System.out.print("sum of three side is:"+perimeter);    }}//exercise 3.27package thirdchapterexercise3;import java.util.Scanner;public class fourth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.print("Enter a point‘s x- and y-coordinates:");        double x=in.nextDouble();        double y=in.nextDouble();        double distance1=Math.pow((x*x+y*y), 0.5);        double distance2=Math.pow((x-200)*(x-200)+(y-100)*(y-100),0.5);        if(distance1>distance2||x>200||x<0||y>100||y<0)            System.out.print("The point is not in the triangle");        else             System.out.print("The point is in the triangle");    }}//exercise 3.28package thirdchapterexercise3;import java.util.Scanner;public class fifth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in =new Scanner(System.in);        System.out.println("Enter r1‘s center x-,y-coordinates,width,and height:");        double x1=in.nextDouble();        double y1=in.nextDouble();        double w1=in.nextDouble();        double h1=in.nextDouble();        System.out.println("Enter r2‘s center x-,y-coordinates,width,and height:");        double x2=in.nextDouble();        double y2=in.nextDouble();        double w2=in.nextDouble();        double h2=in.nextDouble();                double insidelimitwidth=Math.abs(w1-w2);        double insidelimitheight=Math.abs(h1-h2);                double insidejudgewidth=Math.abs(x2-x1);        double insidejudgeheight=Math.abs(y2-y1);                        double overlapslimitwidth=w1+w2;        double overlapslimitheight=h1+h2;                double overlapsjudgewidth=Math.abs(x2-x1);        double overlapsjudgeheight=Math.abs(y2-y1);                if (insidejudgewidth<insidelimitwidth&&insidejudgeheight<insidelimitheight)            System.out.println("r2 is inside r1");        else if (overlapsjudgewidth<overlapslimitwidth&&overlapsjudgeheight<overlapslimitheight)            System.out.println("r2 overlaps r1");        else             System.out.println("r2 does not overlap r1");            }}//exercise 3.29package thirdchapterexercise3;import java.util.Scanner;public class sixth {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in=new Scanner(System.in);        System.out.println("Enter circle1‘s center x-,y-coordinates,and radius:");        double x1=in.nextDouble();        double y1=in.nextDouble();        double r1=in.nextDouble();        System.out.println("Enter circle2‘s center x-,y-coordinates,and radius:");        double x2=in.nextDouble();        double y2=in.nextDouble();        double r2=in.nextDouble();                double distance=Math.pow((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2),0.5);                double insidelimit=Math.abs(r1-r2);        double overlapslimit=r1+r2;                if(distance<insidelimit)            System.out.println("circle2 is inside circle1");        else if (distance<overlapslimit)            System.out.println("circle2 overlaps circle1");        else             System.out.println("circle2 does not overlap circle1");                    }}