Java数组学习之前基础小案例

不多说,1天时间看完数组之前内容,这就靠代码的实践总结一下吧~~

打印三角形

简单易懂,初学都会,就不注释了,前者为取巧的三角形实现方法,我注释了,直接上源码~~

public class Triangle {
public void triangle(){
/*for (int i = 0; i < 9; i++) {
for (int j = 9; j > i; j--) {
System.out.print(" ");
}
for (int j = 0; j < i; j++) {
System.out.print("* ");
}
System.out.println();
}*/
for (int i = 0; i < 9; i++) {
for (int j = 9; j > i; j--) {
System.out.print(" ");
}
for (int j = 0; j < i; j++) {
System.out.print("* ");
}
for (int j = i-1; j > 0; j--) {
System.out.print("* ");
}
System.out.println();
}
}
}


打印九九乘法表

不多说,上代码~~

public class Multiplication {
public void multiplication(){
for (int i = 1; i <= 9; i++) {
for (int j = 1; j <= i; j++) {
System.out.print(i+"*"+j+"="+i*j+"\t");
}
System.out.println();
}
}
}


将数组转化为稀疏数组,以及将稀疏数组转化为正常数组

public class SparseArray {
public int[][] sparseArray(int[][] a){
//记录有效数字,定义count变量记录
int count=0; for (int i = 0; i < a.length ; i++) {
for (int j = 0; j < a[i].length; j++) {
if (a[i][j] != 0)
count++;
}
}
//System.out.println(count);
int[][] a2 = new int[count+1][3];
a2[0][0] = a.length;
a2[0][1] = a[0].length;
a2[0][2] = count;
//count变量此时计数用,重置为0
count = 0;
//遍历数组存储为稀疏数组
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
if (a[i][j] != 0)
{
++count;
a2[count][0] = i;
a2[count][1] = j;
a2[count][2] = a[i][j];
}
}
}
return a2;
}
}


稀疏数组转化为正常数组

public class RestoreArrays {
public int[][] restoreArrays(int[][] a){
int[][] a2 = new int[a[0][0]][a[0][1]];
for (int i = 1; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
a2[a[i][0]][a[i][1]] = a[i][j];
}
}
return a2;
}
}


以及打印输出二维数组

public class OutArrays {
public void outArrays(int[][] a){
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
System.out.print(a[i][j]+"\t");
}
System.out.println();
}
}
}


实现的效果