数组
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声明数组变量
public class ArrayTest {
public static void main(String[] args) {
int[] array1 = new int[5];
int[] array2;
array2 = new int[5];
int[] array3 = {1,2,3,4,5};
System.out.print("array1:");
for (int i = 0; i < 5; i ++)
System.out.print(array1[i] + " ");
System.out.printf("/narray2:");
for (int i = 0; i < array2.length; i ++)
System.out.print(array2[i] + " ");
System.out.printf("/narray3:");
for (int arr : array3)
System.out.print(arr + " ");//JDK5.0
System.out.println();
}
}
输出结果：
array1:0 0 0 0 0
array2:0 0 0 0 0
array3:1 2 3 4 5
动态申请数组长度
import java.util.Scanner;
public class ArrayLength {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Please input the length:");
int length = scanner.nextInt();
int[] array = new int[length];
for (int arr : array)
System.out.print(arr + " ");
System.out.println();
}
}
输出结果：
Please input the length:10
0 0 0 0 0 0 0 0 0 0
二维数组
public class TwoDimArray {
public static void main(String[] args) {
int[][] array1 = {
{1,2,3},{4,5,6}
};
int[][] array2 = new int[3][4];
for (int i = 0; i < array1.length; i ++)
for (int j = 0; j < array1[i].length; j ++)
System.out.print(array1[i][j] + " ");
System.out.println();
for (int[] row : array2)
for (int b : row)
System.out.print(b + " ");
System.out.println();
}
}
不规则数组
public class LotteryArray {
public static void main(String[] args) {
int[][] array1 = new int[2][];
array1[0] = new int[5];
array1[1] = new int[10];
for (int i = 0; i < array1.length; i ++)
{
for (int j = 0; j < array1[i].length; j ++)
System.out.print(array1[i][j] + " ");
System.out.println();
}
}
}
输出结果；
0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
public class LotteryArrayTest {
public static void main(String[] args) {
final int MAX = 10;
int[][] odds = new int[MAX+1][];
for (int i = 0; i <= MAX; i ++)
odds[i] = new int[i+1];
for (int i = 0; i < odds.length; i ++)
for (int j = 0; j < odds[i].length; j ++)
{
int lotteryodds = 1;
for (int k = 1; k <= j; k ++)
lotteryodds = lotteryodds *(i-k+1)/k;
odds[i][j] = lotteryodds;
}
for (int[] row : odds)
{
for (int odd : row)
System.out.printf("%4d",odd);
System.out.println();
}
}
}
输出结果：
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1 6 15 20 15 6 1
1 7 21 35 35 21 7 1
1 8 28 56 70 56 28 8 1
1 9 36 84 126 126 84 36 9 1
1 10 45 120 210 252 210 120 45 10 1
数组进阶
public class AdvanceArray {
public static void main(String[] args) {
int[] array = new int[]{1,2,3,4,5};
int[] temp;
temp = array;
for (int a : array)
System.out.print(a + " ");
System.out.println();
for (int t : temp)
System.out.print(t + " ");
System.out.println();
temp[3] = 0;
for (int a : array)
System.out.print(a + " ");
System.out.println();
for (int t : temp)
System.out.print(t + " ");
System.out.println();
}
输出结果：
1 2 3 4 5
1 2 3 4 5
1 2 3 0 5
1 2 3 0 5
array和temp引用自同一对象，对两者的操作都会改变其指向的值。
数组拷贝
System.arraycopy(from, fromIndex, to, toIndex, count);
将第一个数组的第fromIndex个位置开始拷贝count个元素，目标数组
起始位置为toIndex
System.arraycopy(来源, 起始索引, 目的, 起始索引, 复制长度);
public class CopyArray {
public static void main(String[] args) {
int[] array1 = new int[]{1,2,3,4,5};
int[] array2 = new int[5];
int[] array3 = new int[5];
int[] array4 = new int[] {11,12,13,14,15};
for (int i = 0; i < array1.length; i ++)
array2[i] = array1[i];
System.arraycopy(array1, 0, array3, 0, array1.length);
System.arraycopy(array1, 1, array4, 2, 3);
for (int arr : array2)
System.out.print(arr + " ");
System.out.println();
for (int arr : array3)
System.out.print(arr + " ");
System.out.println();
for (int arr : array4)
System.out.print(arr + " ");
}
}
输出结果：
1 2 3 4 5
1 2 3 4 5
11 12 2 3 4
