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JAVA学习第三天

2015-07-16 10:23 513 查看

1+3+7+…..+(2^20)-1

import java.util.Scanner;
public  class Demo3Day{
public   static void main(String[]  args){
//      int  s=0;
//      int  x=1;
//      int  k=0;
//      for(int i=0;i<=19;i++){
//          x<<=1;  只用移一位即可
//          s=s+x-1;
//          }
//      System.out.println(s);
//
int  s=0;
int  a=1;
for(int i=1;i<=20;i++){
a=a*2;
s=s+(a-1);
}
System.out.println(s);
}
}

1+2+4+…+12+14+…+10000(尾数为三的忽略掉)

import java.util.Scanner;

public class Demo3Day {
public static void main(String[] args) {

int s = 0;

for (int i = 1; i <= 10000; i++) {
// if(i%10!=3){
//
// s=s+i;
// }
//
// }
if (i % 10 == 3) {
continue;
}
s+=i;
}
System.out.println(s);

}
}

*号金字塔

int  count=10;
for(int i=1;i<=count;i++){
for(int j=1;j<=(count-i);j++){
System.out.print(' ');
}

for (int l = 1; l<= (2*i-1); l++) {

System.out.print("*");

}
System.out.print("\n");
}
}
}

package com.donghe.svn;

public class Test {
public static void main(String[] args) {
int count = 4;
for (int i = 1; i <= count; i++) {
for (int k = 1; k <= (count - i); k++) {
System.out.print(" ");
}

for (int j = 1; j <= (2 * i - 1); j++) {
if(j==1||j==2||j==(2*i-1)||j==(2*i-2)){
System.out.print("*");
}else{
System.out.print(" ");
}
}
System.out.println();

}
for(int i=(count-1);i>=1;i--){
for(int l=1;l<=(count-i);l++){
System.out.print(' ');
}
for(int j=1;j<=(2*i-1);j++){
if(j==1||j==2||j==(2*i-1)||j==(2*i-2)){
System.out.print("*");
}else{
System.out.print(" ");
}
}
System.out.println();
}

}

}

可改变金字塔大小以及镂空大小

package com.zhonghang.svn;

import java.util.Scanner;

public class Test4 {

public static void main(String[] args) {
int count=5;
int indexMax = 10;
if(count<=indexMax-1){
for (int i = 1; i <= indexMax; i++) {
for (int j = 1; j <= indexMax - i; j++) {
System.out.print(" ");
}

for (int j = 1; j <= (2 * i - 1); j++) {

if ((j >= 1 && j <= count) ||(j <= (2 * i - 1) && j >= (2 * i - count))) {

System.out.print("*");
} else {
System.out.print(" ");
}
}
System.out.println();

}
for (int i = indexMax - 1; i >= 1; i--) {
for (int j = 1; j <= indexMax - i; j++) {
System.out.print(" ");
}

for (int j = 1; j <= (2 * i - 1); j++) {

if ((j >= 1 && j <= count) ||(j <= (2 * i - 1) && j >= (2 * i - count))) {

System.out.print("*");
} else {
System.out.print(" ");
}
}
System.out.println();

}
}
else{
System.out.println("输入的count有误!");
}
}
}

九九乘法表

public class Demo3Day {
public static void main(String[] args) {

int  count=9;
for (int i = 1; i <= count; i++) {
for (int j = 1; j <=i; j++) {
System.out.print(j+"x"+i+"="+i*j+"\t");

}
System.out.println();

}

}
}

1~1000以内的素数

import java.util.Scanner;

public class Demo3Day {
public static void main(String[] args) {

for (int i = 2; i < 1000; i++) {
boolean issushu = true;
for (int j = 2; j < i; j++) {

if (i % j == 0) {
issushu = false;
break;

}
}
if (issushu) {
System.out.println(i);
}
}

}
}

//1~1000完全数   例如:28=1x2x4x7x14   1+2+4+7+14=28
import java.util.Scanner;

public class Demo3Day {
public static void main(String[] args) {

for (int i = 1; i <= 1000; i++) {
int s = 0;//位置很重要 需要将s至零
for (int j = 1; j < i; j++) {
if (i % j == 0) {
// j是i的因子

s += j;
}

}
if (s == i) {
System.out.println(i);
}
}

}
}

import java.util.Scanner;

public class Demo3Day {
public static void main(String[] args) {
int d=0;
int a=1;
int b=2;
int c=3;

for(int i=4;i<=20;i++){
d=a+c;
a=b;
b=c;
c=d;
System.out.println("第"+i+"个月"+"存在的兔子数"+d);

}

}
}