java数组

Java两大类数据类型：1.原始/基本/简单：8种

                                    2.引用/复合类型：数组（int，String）

区别：内存存贮结构1——栈   2——堆，栈

1.奇数数组

class aa {public static void main(String args[]) {/* * int j=0; int[] v=new int[5000]; for(int i=1;i<10000;i++){ if(i%2==1) * {v[j]=i;j++;}} for(j=0;j<v.length;j++) System.out.println(v[j]); */int[] a = new int[50000];for (int i = 0; i < a.length; i++) {a[i] = i * 2 + 1;System.out.println(a[i]);}}}

 

1. 创建一个1-100之间的 素数数
          (只能被1和它本身整除的数字)

   class number4_2 {public static void main(String args[]) {int count = 0;int[] v = new int[50];for (int i = 2; i <= 100; i++) {boolean x = true;for (int j = 2; j < i / 2; j++) {//i/2减少循环次数if (i % j == 0) {x = false;break;}}if (x) {//放在循环外，全跑完才知道找没找到（上面的if语句从来没执行过）v[count++] = i;}}for (count = 0; count < v.length; count++)System.out.println(v[count]);}}

   
    

public class number4_3 {public static void main(String[] argint[] a={1,2,3,4,5};int[] b={4,5,6,7,8};int[] c=new int[a.length+b.length];int[] w=a;for(int i=0;i<c.length;i++){if(i==a.length)  w=b;c[i]=w[i%a.length];System.out.println(c[i]);}} }

i==a.length 只交换一次，i>=a.length  交换多次

i%a.length 利用循环

通过改变数组的栈来改变数组w，使其由数组a变为数组b，从而不使用if else；

3.a = {1,2,3,4,5}和b = {4,5,6,7,8}
        元素合并

class number4_3 {public static void main(String args[]) {int[] a = { 1, 2, 3, 4, 5 };int[] b = { 4, 5, 6, 7, 8 };int[] c = new int[10];for (int i = 0; i < a.length + b.length; i++) {if (i < a.length)c[i] = a[i];if (i >= a.length)c[i] = b[i - a.length];}for (int i = 0; i < c.length; i++) {System.out.println(c[i]);}}}

<span style="font-size:18px;">public class number4_4 {public static void main(String[] args) {int[] a={1,2,3,4,5};int[] b={4,5,6,7,8};int[] w=a;a=b;b=w;for(int i=0;i<a.length;i++){System.out.println(a[i]);}for(int i=0;i<b.length;i++){System.out.println(b[i]);}}}</span>

• int[] x={1,2,3,4,5}
  栈（数组的内存地址）     |      堆（具体的元素）
• 数组交换时可以只改变栈，不改变堆

1. 数组元素交换
   

   class number4_4 {public static void main(String args[]) {int[] a = { 1, 2, 3, 4, 5 };int[] b = { 4, 5, 6, 7, 8 };int[] temp = new int[5];for (int i = 0; i < a.length; i++) {temp[i] = a[i];a[i] = b[i];b[i] = temp[i];}for (int i = 0; i < a.length + b.length; i++) {if (i < a.length)System.out.println(a[i]);elseSystem.out.println(b[i - a.length]);}for (int i = 0; i < a.length; i++) {temp[i] = a[i];a[i] = b[b.length - i - 1];b[b.length - i - 1] = temp[i];}for (int i = 0; i < a.length + b.length; i++) {if (i < a.length)System.out.println(a[i]);elseSystem.out.println(b[i - a.length]);}}}

   
   

2. 找数

   class number4_5{public static void main(String args[]){int[] a={3,4,5,6,7,8};int w=9;boolean x=true;for(int i=0;i<a.length;i++){if(a[i]==w){x=false;System.out.println(w+"在数组中");break;}}if(x) System.out.println(w+"不在数组中");}}