第八周

1.给定一个有9个整数（1,6,2,3,9,4,5,7,8）的数组，先排序，然后输出排序后的数组的值。

package test;
import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;
public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
int a[] = {1,6,5,7,8,9,4,3,2, };
Arrays.sort(a);
for(int i:a) {
System.out.print(" "+i);
}}}

 2.输出一个double型二维数组（长度分别为5、4，值自己设定）的值。

package test;
import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;
public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
double a[][]=new double[5][4];
for (int i = 0; i<a.length;i++) {
for (int j = 0;j<a [i].length; j++) {
a[i][j]=i+j;}}
for (int i = 0;i<a.length;i++) {
for (int j = 0;j<a [i].length; j++) {
System.out.print(a[i][j]+"");}}
System.out.println();}}

 3.在一个有8个整数（18，25，7，36，13，2，89，63）的数组中找出其中最大的数及其下标

package test;
import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;
public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] a= {18,25,7,36,13,2,89,63};
int max = a[0],maxid = 0;
for(int i=1;i<a.length;i++) {
if(max<a[i] ){
max=a[i];
maxid=i;}}
System.out.print("最大数是:"+max+"其下标为:"+maxid);}}

 4. 将一个数组中的元素逆序存放

package test;
import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;
public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] a= {1,3,2,4,6,7,8};
int b;
for(int i=0;i<a.length/2;i++) {
b=a[i];
a[i]=a[a.length-i-1];
a[a.length-i-1]=b;}
for(int i:a) {
System.out.print(i+" ");}
System.out.println();}}

 5.将一个数组中的重复元素保留一个其他的清零

package test;

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] a = { 1, 1, 2, 2, 3, 3, 4, 4,5,5,6,6,7,8 };
boolean[] b = new boolean[a.length];
for (int i = 0; i < a.length - 1; i++) {
if (b[i]) {
continue;
}
for (int j = i + 1; j < a.length; j++) {
if (a[i] == a[j] && !b[j]) {
b[j] = true;
}
}
}
for (int i = 0; i < a.length; i++) {
if (b[i])
continue;
System.out.print(a[i] + " ");
}
System.out.println();
}
}

 6.给定一维数组{ -10，2，3，246，-100，0，5}，计算出数组中的平均值、最大值、最小值。

package test;

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
int a[] = { -10, 2, 3, 246, -100, 0, 5 };
int max = a[0];
int min = a[0];
double sum = 0;
for (int i = 1; i < a.length; i++) {
if (a[i] > max) {
max = a[i];
}
if (a[i] < min) {
min = a[i];
}
}
for (int i = 0; i < a.length; i++) {
sum += a[i];
}
System.out.println("最大值为:" + max);
System.out.println("最小值为:" + min);
System.out.println("平均值为:" + sum / a.length);
}
}

 7.使用数组存放裴波那契数列的前20项 ，并输出

package test;

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] a = new int[20];
a[0] = 1;
a[1] = 1;
for (int i = 2; i < a.length; i++) {
a[i] = a[i - 1] + a[i - 2];
}
for (int i : a) {
}
for (int i : a) {
System.out.println(i);
}
}
}

 8.生成一个长度为10的随机整数数组（每个数都是0-100之间），输出，排序后，再输出

package test;

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

public class acc {
public static void main(String[] args) {
// TODO Auto-generated method stub
Random r = new Random();
int[] a = new int[10];
System.out.println("输出数组为");
for (int i = 0; i < a.length; i++) {
int b = r.nextInt(101);
a[i] = b;
System.out.print(" " + a[i]);
}
Arrays.sort(a);
System.out.println("\n排序后的数组为");
for (int i = 0; i < a.length; i++) {
System.out.print(" " + a[i]);
}
}
}

 9.做一个菜单切换程序。主菜单1.登陆 2.注册 3幸运抽奖 4 退出。每个菜单可以返回主菜单

package test;

import java.util.Random;
import java.util.Scanner;

public class abc { public static void Menu_main() {
Scanner input=new Scanner(System.in);
System.out.println("\t主菜单");
System.out.println("1.登录");
System.out.println("2.注册");
System.out.println("3.幸运抽奖");
System.out.println("4.退出");
int num=input.nextInt();
switch(num) {
case 1:
Menu_1();
break;
case 2:
Menu_2();
break;
case 3:
Menu_3();
break;
case 4:
break;
default :
System.out.println("输入错误");
break;
}
}
public static void Menu_1()
{
Scanner input=new Scanner(System.in);
System.out.println("\t登录");
System.out.println("返回主菜单：1");
System.out.println("退出：2");
int num=input.nextInt();
switch(num) {
case 1:
Menu_main();
case 2:
return;
}
}
public static void Menu_2()
{
Scanner input=new Scanner(System.in);
System.out.println("\t注册");
System.out.println("返回主菜单：1");
System.out.println("退出：2");
int num=input.nextInt();
switch(num) {
case 1:
Menu_main();
case 2:
return;
}
}
public static void Menu_3()
{
Scanner input=new Scanner(System.in);
System.out.println("\t幸运抽奖");
System.out.println("返回主菜单：1");
System.out.println("退出：2");
int num=input.nextInt();
switch(num) {
case 1:
Menu_main();
case 2:
return;
}
}
public static void main(String[] args) {
Menu_main();
}

}