1.用循环的嵌套,输出输出如下图形
*
* * *
* * * * *
* * * * * * *
* * * * *
* * *
*
package Exercises.One_Hundred;
public class Demo01 {
public static void main(String[] args) {
for(int i=1;i<5;i++){
for(int j=1;j<=2*i-1;j++){
System.out.print("*");
}
System.out.println();
}
for(int i=3;i>0;i--){
for(int j=0;j<2*i-1;j++){
System.out.print("*");
}
System.out.println();
}
}
}
2.写一段程序对数组int[] array内的元素从小到大重新排列
package Exercises.One_Hundred;
import java.util.Scanner;
public class Demo02 {
public static void main(String[] args) {
int s=0;
Scanner scanner=new Scanner(System.in);
System.out.println("输入数组长度");
s=scanner.nextInt();
int []array=new int[s];
System.out.println("输入数组元素");
for(int i=0;i<s;i++){
array[i]=scanner.nextInt();
}
System.out.println("排列后数组为:");
int temp;
for(int i=0;i<s-1;i++){
for(int j=0;j<s-1-i;j++){
if(array[j]>array[j+1]){
temp=array[j];
array[j]=array[j+1];
array[j+1]=temp;
}
}
}
for(int i=0;i<s;i++){
System.out.print(array[i]+" ");
}
}
}
或者用Arrays类中sort方法
package Exercises.One_Hundred;
import java.util.Arrays;
import java.util.Scanner;
public class Demo02 {
public static void main(String[] args) {
int s=0;
Scanner scanner=new Scanner(System.in);
System.out.println("输入数组长度");
s=scanner.nextInt();
int []array=new int[s];
System.out.println("输入数组元素");
for(int i=0;i<s;i++){
array[i]=scanner.nextInt();
}
System.out.println("排列后数组为:");
Arrays.sort(array);
for(int i=0;i<s;i++) {
System.out.print(array[i] + " ");
}
}
}
3.求 2/1+3/2+5/3+8/5+13/8.....前20项之和?
package Exercises.One_Hundred;
public class Demo03 {
public static void main(String[] args) {
double fm,fz=2;
double sum=0,temp=0;
for(fm=1;fm<=20;fm++){
temp=fz/fm;
sum+=temp;
fz=fz+fm;
}
System.out.println(sum);
}
}
4.计算圆周率:
package Exercises.One_Hundred;
public class Demo04 {
public static void main(String[] args) {
System.out.println(Math.PI);
}
}
5.定义两个数3和10,输出大数和小数
package Exercises.One_Hundred;
public class Demo05 {
public static void main(String[] args) {
int a=3;
int b=10;
if(a>b){
System.out.println("大数为:"+a);
System.out.println("小数为:"+b);
}else {
System.out.println("大数为:"+b);
System.out.println("小数为:"+a);
}
}
}
6.用if..else语句,判断一个数字是奇数还是偶数
package Exercises.One_Hundred;
import java.util.Scanner;
public class Demo06 {
public static void main(String[] args) {
int a;
Scanner scanner=new Scanner(System.in);
System.out.println("请输入一个整数");
a=scanner.nextInt();
if(a%2==0){
System.out.println(a+"是偶数");
}else{
System.out.println(a+"是奇数");
}
}
}
\7. 定义两个数3和10,用三目运算符输出最大数
package Exercises.One_Hundred;
public class Demo07 {
public static void main(String[] args) {
int a=3;
int b=10;
int max = 0;
max=a>b?a:b;
System.out.println(max);
}
}
\8. 定义两个数3和10,用if语句输出最大数
package Exercises.One_Hundred;
public class Demo08 {
public static void main(String[] args) {
int a=3;
int b=10;
if(a>b){
System.out.println(a);
}else{
System.out.println(b);
}
}
}
9.用while输出1+2+......+10的和
package Exercises.One_Hundred;
public class Demo09 {
public static void main(String[] args) {
int i=1;
int sum=0;
while (i<=10){
sum+=i;
i++;
}
System.out.println(sum);
}
}
10.用do while语句 输出1+2+......+10的和
package Exercises.One_Hundred;
public class Demo10 {
public static void main(String[] args) {
int i=1;
int sum=0;
do{
sum+=i;
i++;
}while (i<=10);
System.out.println(sum);
}
}
\11. 用for语句 输出1+2+......+10的和
package Exercises.One_Hundred;
public class Demo11 {
public static void main(String[] args) {
int sum=0;
for(int i=1;i<=10;i++){
sum+=i;;
}
System.out.println(sum);
}
}
12.输出1-100之间不能被3整除的数
package Exercises.One_Hundred;
public class Demo12 {
public static void main(String[] args) {
for(int i=1;i<=100;i++){
if(i%3!=0){
System.out.println(i);
}
}
}
}
13.定义数组,数组元素的值为67,89,87,69,90,100,75,90,用循环找出数组的最大数和最小数
package Exercises.One_Hundred;
public class Demo13 {
public static void main(String[] args) {
int[]array={67,89,87,69,90,100,75,90};
int max=array[0];
int min=array[array.length-1];
for(int i=0;i<array.length;i++){
if(array[i]>max){
max=array[i];
}
if(array[i]<min){
min=array[i];
}
}
System.out.println("最大值为"+max+" 最小值为"+min);
}
}
14.定义方法addInt()和addFloat(),第一个方法能求两个整数的和, 第二个方法能求两个实数的和,写测试类,调用这两个方法
package Exercises.One_Hundred;
public class Demo14 {
public static int addInt(int a,int b){
return a+b;
}
public static double addFloat(double a,double b){
return a+b;
}
public static void main(String[] args) {
System.out.println(addInt(3, 10));
System.out.println(addFloat(3.5, 4.7));
}
}
15.用递归方法求5!
package Exercises.One_Hundred;
public class Demo15 {
public static int f(int s){
if(s==1||s==0){
return 1;
}
return s*f(s-1);
}
public static void main(String[] args) {
System.out.println(f(5));
}
}
16.定义Person类,Person类有name和age属性,有方法tell()输出Person实例的姓名和年龄,定义测试类,创建Person对象person他的名字叫Tom,年龄18,person调用tell()方法输出它的姓名和年龄
package Exercises.One_Hundred.Dem016;
public class Person {
String name;
int age;
public void tell(){
System.out.println(name+" "+age);
}
}
package Exercises.One_Hundred.Dem016;
public class test {
public static void main(String[] args) {
Person person=new Person();
person.name="Tom";
person.age=18;
person.tell();
}
}
\17. 定义Person类,Person类有name和age属性,
有方法tell()输出Person实例的姓名和年龄,
有构造方法实现对域的初始化
定义测试类,创建Person对象person他的名字叫Tom,年龄18,person调用tell()方法输出它的姓名和年龄
package Exercises.One_Hundred.Demo17;
public class Person {
String name;
int age;
public Person(String name,int age){
this.name=name;
this.age=age;
}
public void tell(){
System.out.println(name+" "+age);
}
}
package Exercises.One_Hundred.Demo17;
import Exercises.One_Hundred.Dem016.Person;
public class test {
public static void main(String[] args) {
Person person=new Person("Tom",18);
person.tell();
}
}
\18. 定义父类Person和子类Student,父类有非私有的name和age,有两个构造方法,一个是无参的构造方法,一个是有参的构造方法,子类有自己的属性school,有无参的和有三个参数的构造方法
package Exercises.One_Hundred.Demo18;
public class Person {
String name;
int age;
public Person(){
}
public Person(String name,int age){
this.name=name;
this.age=age;
}
}
package Exercises.One_Hundred.Demo18;
public class Student extends Person{
String school;
public Student(){
}
public Student(String name,int age,String school){
this.name=name;
this.age=age;
this.school=school;
}
}
\19. 定义父类Person和子类Student,父类有非私有的name和age,有两个构造方法,一个是无参的构造方法,一个是有参的构造方法,子类有自己的属性school,有无参的和有三个参数的构造方法,其中第二个构造方法在初始化时要调用父类的构造方法
package Exercises.One_Hundred.Demo19;
public class Person {
String name;
int age;
public Person(){
}
public Person(String name,int age){
this.name=name;
this.age=age;
}
}
package Exercises.One_Hundred.Demo19;
public class Student extends Person{
String school;
public Student(){
}
public Student(String name,int age,String school){
Person person=new Person(name,age);
this.school=school;
}
}
\20. 定义抽象父类Person,子类Student,父类有非私有的name和age,有两个构造方法,一个是无参的构造方法,一个是有参的构造方法,有一个抽象的方法String getInfo(),子类有自己的属性school,有无参的和有三个参数的构造方法,要求在子类中重写抽象方法,并输出子类的各项信息
package Exercises.One_Hundred.Demo18.Demo20;
public abstract class Person {
String name;
int age;
public Person(){
}
public Person(String name,int age){
this.name=name;
this.age=age;
}
public abstract String getInfo();
}
package Exercises.One_Hundred.Demo18.Demo20;
public class Student extends Person{
String school;
public Student(){
}
public Student(String name,int age,String school){
this.name=name;
this.age=age;
this.school=school;
}
@Override
public String getInfo() {
return name+" "+age+" "+school;
}
}