java学习日志（二）-- 循环Loop实验

public class OddNumber {
public static void main(String[] args) {
for (int num = 1;  num <= 200; num++) {
if (num % 2 != 0){ //判断是否为奇数
System.out.print(num + "\t");
}
if (num % 20 == 0){ //输出十个奇数换一行
System.out.println();
}
}
}
}

public class MultiplicationTable
{
public static void main(String[] args)
{
for (int  = 1; i <= 9 ; i++ )
{
for (int j = 1; j <= i; j++ )
{
System.out.print(j + "*" + i +"=" + i  * j + "\t");
}
System.out.println();
}
}
}

public class  LetterTriangle
{
public static void main(String[] args)
{
char[] arr = new char[]{'A','B','C','D','E','F','G'};
for(int i = 0; i < 7; i++){
for (int j = 0; j < 6-i ;j++ )
{
System.out.print("  ");
}
for(int k = 0; k < 2*i+1; k++){
System.out.print(arr[i]+" ");
}
System.out.println();
}
}
}

import java.util.Scanner;

public class AddDigit
{
public static void main(String[] args) {
Scanner in  = new Scanner(System.in);
System.out.print("请输入一个五位整数：");
int i = in.nextInt();
int sum = 0;
if (i < 10000 || i > 99999) {
System.out.println("输入有误！");
} else {
for (int j = 0; j < 5  ; j++ ) {
sum +=  i % 10;
i = i / 10;
}
System.out.println("该五位整数各位数上之和为sum=" + sum );
}

System.out.print("请输入一个五位整数:");
int n = in.nextInt();
int m = 0;
for (int k = 10000 ; k > 0 ; k /= 10 ) {
m +=  n  /  k ;
n %= k;
}
System.out.println("该五位整数各位数上之和为:" + m);

System.out.print("请输入一个整数：");
int j = in.nextInt();
int s = 0;
while(j != 0) {
s +=  j % 10;
j = j / 10;
}
System.out.println("该整数各位数上之和为s=" + s );
}
}

import java.util.Scanner;

public class GuessNum
{
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int number = (int) (Math.random() * 100 + 1); //random()返回带正号的 double 值，该值大于等于 0.0 且小于 1.0。[0,1.0)-->[1,100]
int x;
int count = 0;
do {
System.out.print("请输入一个1-100间的整数：");
x = in.nextInt();
count++;
if (x > number) {
System.out.println("\t\t\t\t\t偏大");
} else if (x < number) {
System.out.println("\t\t\t\t\t偏小");
}
} while (x != number);
System.out.println("\t\t\t恭喜你，猜对了，你猜了" + count + "次");
}
}

import java.util.Arrays;

public class Sort
{
public static void main(String[] args){

int[] arr = { 4, 5, 6, 23, 1, 3};
selectSort(arr);
printArr(arr);

int[] ar = { 4, 5, 6, 23, 1, 3};
bubbleSort(ar);
printArr(ar);

int[] a = { 4, 5, 6, 23, 1, 3};
System.out.println("自带排序方法：");
Arrays.sort(a);
printArr(a);
}

//选择排序
public static void selectSort(int[] arr){
System.out.println("选择排序分步结果：");
for(int x = 0; x < arr.length - 1; x++){
for(int y = x + 1; y < arr.length; y++){
if(arr[x] > arr[y]){
printArr(arr);
int temp = arr[x];
arr[x] = arr[y];
arr[y] = temp;

}
}
}
}

//冒泡排序
public static void bubbleSort(int[] arr){
System.out.println("冒泡排序分步结果：");
for (int x = 0; x < arr.length -1; x++) //for(int x=arr.length-1; x>0; x--)
{
for(int y = 0; y < arr.length - x -1; y++){ //-x:让每一次比较的元素减少， -1：避免角标越界
if (arr[y] > arr[y+1])
{
printArr(arr);
int temp = arr[y];
arr[y] = arr[y+1];
arr[y+1] = temp;

}
}
}
}

//打印数组
public static void printArr(int[] arr){
System.out.print("\t\t[ ");
for(int i : arr){
System.out.print(i + " ");
}
System.out.println("]");
}
}