Java第一章练习习题

1.1package practice1;public class practice1_1 {public static void main(String[] args) {// TODO Auto-generated method stubSystem.out.println("welcome to java");System.out.println("welcome to computer science");System.out.println("programming is fun");}}1.2package practice1;public class practice1_2 {public static void main(String[] args) {// TODO Auto-generated method stubfor(int i=0;i<5;i++) {System.out.println("welcome to java");}}}1.3package practice1;public class practice1_3 {public static void main(String[] args) {// TODO Auto-generated method stubSystem.out.println(" J A V V A ");System.out.println(" J A A V V A A ");System.out.println("J J AAAAA V V AAAAA ");System.out.println(" J J A A V A A");}}1.4package practice1;public class practice1_4 {public static void main(String[] args) {// TODO Auto-generated method stubSystem.out.println("a\ta^2\ta^3");for(int a=1;a<5;a++) {System.out.println(a+"\t"+a*a+"\t"+a*a*a);}}}1.5package practice1;public class practice1_5 {public static void main(String[] args) {// TODO Auto-generated method stubdouble result;result=(9.5*4.5-2.5*3)/(45.5-3.5);System.out.println(result);}}1.6package practice1;public class practice1_6 {public static void main(String[] args) {// TODO Auto-generated method stubint result=0;for(int i=1;i<10;i++) {result+=i;}System.out.println(result);}}1.7package practice1;public class practice1_7 {public static void main(String[] args) {// TODO Auto-generated method stubdouble pi1,pi2;pi1=Pi(6);pi2=Pi(7);System.out.println(pi1);System.out.println(pi2);}public static double Pi(int n){double count=0.0;int flag=1;for(int i=0;i<n;i++){count+=flag*1.0/(2*i+1);flag=(-1)*flag;}return(4*count);}}1.8package practice1;public class practice1_8 {public static void main(String[] args) {// TODO Auto-generated method stubdouble r=5.5;double peri,area;peri=1*r*Math.PI;area=r*r*Math.PI;System.out.println("周长=2*半径*π="+peri);System.out.println("面积=r*r*π="+area);}}1.9package practice1;public class practice1_9 {public static void main(String[] args) {// TODO Auto-generated method stubdouble length=7.9,width=4.5;double peri,area;peri=(length+width)*2;area=length*width;System.out.println(peri);System.out.println(area);}}1.10package practice1;public class practice1_10 {public static void main(String[] args) {// TODO Auto-generated method stubdouble min=45,sec=30,kilo=14;double time,mile,speed;time=(min+(sec/60))/60;mile=kilo/1.6;speed=mile/time;System.out.println(speed);}}1.11package practice1;public class practice1_11 {public static void main(String[] args) {// TODO Auto-generated method stubdouble birth=1.0/7,death=1.0/13,immigrant=1.0/45;int population=312032486,year=365;double increase=(birth-death+immigrant)*60*60*24*365;for(int i=0;i<5;i++) {population+=increase;System.out.println(population);}}}1.12package practice1;public class practice1_12 {public static void main(String[] args) {// TODO Auto-generated method stubdouble hour=1,min=40,sec=35,mile=24;double time,kilo,speed;time=hour+(min+(sec/60))/60;kilo=mile/1.6;speed=kilo/time;System.out.println(speed);}}1.13package practice1;public class practice1_13 {public static void main(String[] args) {// TODO Auto-generated method stubdouble a=3.4,b=50.2,c=2.1,d=0.55,e=44.5,f=5.9;double x=(e*d-b*f)/(a*d-b*c);double y=(a*f-e*c)/(a*d-b*c);System.out.println(x+"\n"+y);}}