JAVA 数组专题（韩顺平）
判断下列数组赋值是否正确（答案放在最后面啦）
String str[] = {'a','b','c'};
String str[] = {"a","b","c"};
String str[] = new String[]{"a","b","c"};
String str[] = new String{"a","b","c"};
String str[] = new String[3]{"a","b","c"};一.简单的数组扩容
int[] arr1 = {1,2,3};
int[] arrNew = new int[arr1.length + 1];
for (int i = 0; i < arr1.length; i++) {
arrNew[i] = arr1[i];
}
arrNew[arr1.length] = 5;
arr1 = arrNew;//将arrnew的地址传给arr1后，数组arr1将消失
for (int i = 0; i < arr1.length + 1; i++) {
System.out.println(arrNew[i]);
}
for (int i = 0; i < arr1.length; i++) {
System.out.println(arr1[i]);
}二.连续进行数组扩容
Scanner myscanner = new Scanner(System.in);
int[] arr = {1,2,3};
do {
int[] arrnew = new int[arr.length + 1];
for (int i = 0; i < arr.length; i++) {
arrnew[i] = arr[i];
}
arrnew[arrnew.length - 1] = myscanner.nextInt();
arr = arrnew;
for (int i = 0; i < arrnew.length; i++) {
System.out.println(arrnew[i]);
}
System.out.println("是否继续输入");
char key = myscanner.next().charAt(0);
if (key == 'n') break;//输入n结束扩容
}while (true);三
.数组删减
int[] arr = {1,2,3};
Scanner myscanner = new Scanner(System.in);
do {
int[] newarr = new int[arr.length - 1];
for (int i = 0; i < newarr.length; i++) {
newarr[i] = arr[i];
}
arr = newarr;
char s = myscanner.next().charAt(0);
if (newarr.length == 0 || s == 'n') break;//输入n结束缩减
for (int i = 0; i < newarr.length; i++) {
System.out.println(newarr[i]);
}
}while (true);
四.二维数组静态初始化
int[][] arr = {{1},{2,2},{3,3,3}};//第一个一维数组的括号不能省略
// //1.定义了一个二维数组arr
// //2.arr有三个元素
// //3.第一二数组有三个元素，第三个一维数组有一个数组五.动态二维数组开空间
/*动态创建以下二维数组 i = 0：1 i = 1：2 2 i = 2：3 3 3 */
int[][] arr = new int[3][];//创建了二维数组，一共有三个一维数组，但每个一维数组还没有开空间
for (int i = 0; i < arr.length; i++) {
arr[i] = new int[i + 1];//给每个一位数组开空间
for (int j = 0; j < arr[i].length; j++) {
arr[i][j] = i + 1;//给一维的每个元素赋值
}
}
//遍历输出
for (int i = 0; i < arr.length; i++) {
for (int j = 0; j < arr[i].length; j++) {
System.out.print(arr[i][j] + " ");
}
System.out.println("\n");
}例题1：杨辉三角
Scanner myscanner = new Scanner(System.in);
int n = myscanner.nextInt();
int[][] arr = new int[n][];
for (int i = 0; i < arr.length; i++) {
arr[i] = new int[i + 1];
arr[i][0] = 1;
arr[i][i] = 1;
for (int j = 1; j < i; j++) {
arr[i][j] = arr[i - 1][j] + arr[i - 1][j - 1];
}
}
for (int i = 0; i < arr.length; i++) {
for (int j = 0; j < arr[i].length; j++) {
System.out.print(arr[i][j] + "\t");
}
System.out.print("\n");
}例题2：给一升序数组插入一元素，保证插入后数组仍保证升序排列
int[] arr = {10,12,40,90};
Scanner myscanner = new Scanner(System.in);
do {
int insertnum = myscanner.nextInt();
if (insertnum == 0) break;//输入0扩容结束
int index = -1;
for (int i = 0; i < arr.length; i++) {
if (insertnum <= arr[i]) {
index = i;//确定插入位置
break;
}
}
if (index == -1) {
index = arr.length;//判断插入位置是否为最后一位
}
int[] arrNew = new int[arr.length + 1];
for (int i = 0, j = 0; i < arrNew.length; i++) {
if (i != index) {
arrNew[i] = arr[j++];//将arr数组拷贝到arrNew且跳过index
} else {
arrNew[i] = insertnum;//插入数据
}
}
arr = arrNew;
for (int i = 0; i < arrNew.length; i++) {//遍历输出
System.out.print(arrNew[i] + "\t");
}
}while(true);例题3：冒泡排序
bubble sort
int[] arr = {3,5,2,7,5,4,1,0};
for (int i = 0; i < arr.length - 1; i++) {
for (int j = 0; j < arr.length - 1 - i; j++) {
if (arr[j] > arr[j + 1]){
arr[j] = arr[j] ^ arr[j + 1];
arr[j + 1] = arr[j] ^ arr[j + 1];
arr[j] = arr[j] ^ arr[j + 1];
}
}
}
for (int j = 0; j < arr.length; j++) {
System.out.println(arr[j]);
}例题4：判断下列语句是否正确
String str[] = {'a','b','c'};//error
String str[] = {"a","b","c"};//ok
String str[] = new String[]{"a","b","c"};//ok
String str[] = new String{"a","b","c"};//error
String str[] = new String[3]{"a","b","c"};//error