二维数组的遍历以及四种拷贝方式

例：数组的倒置以及合并

public class TestDemo1 {
    //反转数组
    public static void reverse(int[] array){
        for(int i =0;i<array.length/2;i++){
            int tmp = array[i];
            array[i] = array[array.length-1-i];
            array[array.length-1-i] = tmp;
        }
    }
    //合并数组
    public static void merge(int[] array1,int[] array2){
        int[] array3 = new int[array1.length+array2.length];
        for(int i = 0;i < array1.length;i++){
            array3[i] = array1[i];
        }

        for(int j = 0;j < array2.length;j++){
            array3[array1.length+j] = array2[j];
        }

        for(int k = 0;k < array3.length;k++){
            System.out.print(array3[k]+" ");
        }
        System.out.println();

    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[] array = {12,34,21,22,4,6,81,2,1};
        int[] array2 = {5,8,10};
        reverse(array);
        merge(array,array2);
    }
}

运行结果如下：

二分查找例题

public class TestDemo1 {

    public static int Search(int[] array,int val){
        int low = 0;
        int high = array.length-1;
        while(low<=high){
            //int mid = (low+high)/2;
            //int mid = low+(high-low)/2;
            int mid = (low+high)>>>1;   //下标
            if(array[mid]>val){
                high = mid - 1;
            }else if(array[mid]<val){
                low = mid + 1;
            }else{
                return mid;
            }
        }
        return -(low+1);//源码中为-(low+1)   查找数据的插入点位置
    }
    public static void main(String[] args) {
        int[] array = {12,34,21,22,4,6,81,2,1};
        Arrays.sort(array);
        System.out.println(Arrays.toString(array));
        int index = Arrays.binarySearch(array,12);
        System.out.println(index);
        //binarySearch  二分查找
    }

}

运行结果如下：

二维数组的遍历

基本类型

public static void show1(int[][] array){
        for(int i = 0;i<array.length;i++){
            for(int j = 0;j<array[i].length;j++){
                System.out.println(array[i][j]+" ");
            }
            System.out.println();
        }
    }

引用类型

public static void show2(TestArray[][] Array)
    {
        for (int i = 0; i < Array.length; i++) {
            for (int j = 0; j < Array[i].length; j++) {
                System.out.print(Array[i][j].getA()+"  ");
            }
            System.out.println();
        }
    }

二维数组的创建

public class TestDemo2 {
    public static void show1(int[][] array){
        for(int i = 0;i<array.length;i++){
            for(int j = 0;j<array[i].length;j++){
                System.out.println(array[i][j]+" ");
            }
            System.out.println();
        }
    }

    public static void show2(int[][] array){
        for(int[] brr: array){
            for(int i:brr){
                System.out.print(i+" ");
            }
            System.out.println();
        }
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[][] array = new int[2][3];
        array[0][0] = 100;
        int[][] array2 = {{1,2,3},{4,5,6}};
        int[][] array3 = new int[][]{{1,2,3},{4,5,6}};
        show2(array);
        System.out.println("========");
        show2(array2);
        System.out.println("========");
        show2(array3);
        System.out.println("========");
        //不规则数组
        int[][] array4 = new int[2][];
        array4[0] = new int[3];
        array4[1] = new int[2];
        array4[0][0] = 100;
        show2(array4);
        //System.out.println(array4[0][0]);
        //int[][] array5 = new int[][3];   //格式错误
        }
}

拷贝方式

（1）for循环

基本类型

public class TestDemo3 {

    public static void show1(int[][] array){
        for(int i = 0;i<array.length;i++){
            for(int j = 0;j<array[i].length;j++){
                System.out.print(array[i][j]+" ");
            }
            System.out.println();
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[][] array = {{1,2,3},{4,5,6}};
        int[][] array2 = new int[2][3];
        //for循环拷贝
        for (int i = 0; i < array.length; i++) {         
            for (int j = 0; j < array[i].length; j++) {
                array2[i][j] = array[i][j];
            }
        }
        show1(array);
        System.out.println("========");
        show1(array2);
        array2[0][0] = 100;
        System.out.println("====改变后====");
        show1(array);
        System.out.println("========");
        show1(array2);
        }
}

引用类型

class TestArray{
    private int a=10;

    public int getA() {
        return a;
    }
    public void setA(int a) {
        this.a = a;
    }
}
public class TestDemo3 {
    public static void show2(TestArray[][] Array)
    {
        for (int i = 0; i < Array.length; i++) {
            for (int j = 0; j < Array[i].length; j++) {
                System.out.print(Array[i][j].getA()+"  ");
            }
            System.out.println();
        }
    }
    public static void main(String[] args) {
        TestArray[][] a = new TestArray[2][3];
        TestArray[][] b = new TestArray[2][3];
        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[i].length; j++) {
                a[i][j] = new TestArray();
            }
        }

        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[i].length; j++) {
                b[i][j] = a[i][j];
            }
        }
        show2(a);
        System.out.println("========");
        show2(b);
        b[0][0].setA(1000);
        System.out.println("====改变后====");
        show2(a);
        System.out.println("========");
        show2(b);
    }
}

(2)clone方法

基本类型

public class TestDemo4 {
    public static void show1(int[][] array){
        for(int i = 0;i<array.length;i++){
            for(int j = 0;j<array[i].length;j++){
                System.out.print(array[i][j]+" ");
            }
            System.out.println();
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[][] a = {{1,2,3},{4,5,6}};
        int[][] b = new int[2][3] ;

        for (int i = 0; i < a.length; i++) {
            b[i] = a[i].clone();
        }
        show1(a);
        System.out.println("========");
        show1(b);
        b[0][0] = 100;
        System.out.println("====改变后====");
        show1(a);
        System.out.println("========");
        show1(b);
        System.out.println("========");
        int[] array3 = {1,2,3,4,5};
        int[] array4;
        System.out.println(array3);
        array4 = array3.clone();
        System.out.println(array4);
    }
}

引用类型

class TestArray2{
    private int a=10;

    public int getA() {
        return a;
    }
    public void setA(int a) {
        this.a = a;
    }
}
public class TestDemo4 {
    public static void show2(TestArray[][] Array)
    {
        for (int i = 0; i < Array.length; i++) {
            for (int j = 0; j < Array[i].length; j++) {
                System.out.print(Array[i][j].getA()+"  ");
            }
            System.out.println();
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        TestArray[][] a = new TestArray[2][3];
        TestArray[][] b = new TestArray[2][3];
        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[i].length; j++) {
                a[i][j] =new TestArray();
            }
        }
        for (int j = 0; j < a.length; j++) {
            b[j] = a[j].clone();
        }
        show2(a);
        System.out.println("========");
        show2(b);
        b[0][0].setA(1000);
        System.out.println("====改变后====");
        show2(a);
        System.out.println("========");
        show2(b);
    }
}

（3）System.arraycopy拷贝

基本类型

public class TestDemo6 {
    public static void show1(int[][] array){
        for(int i = 0;i<array.length;i++){
            for(int j = 0;j<array[i].length;j++){
                System.out.print(array[i][j]+" ");
            }
            System.out.println();
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[][] array = {{1,2,3},{4,5,6}};
        int[][] array2 = new int[2][3];
        for(int i = 0 ;i<array.length;i++){
            System.arraycopy(array[i], 0, array2[i], 0, array[i].length);
        }
        show1(array);
        System.out.println("======");
        show1(array2);
        array2[0][0] = 1000;
        System.out.println("====改变后====");
        show1(array);
        System.out.println("======");
        show1(array2);
    }
}

引用类型

class TestArray3{
    private int a=10;
    public int getA() {
        return a;
    }
    public void setA(int a) {
        this.a = a;
    }
}
public class TestDemo6 {
    public static void show2(TestArray3[][] Array)
    {
        for (int i = 0; i < Array.length; i++) {
            for (int j = 0; j < Array[i].length; j++) {
                System.out.print(Array[i][j].getA()+"  ");
            }
            System.out.println();
        }
    }
    public static void main1(String[] args) {
        TestArray3[][] t1 = new TestArray3[2][3];
        TestArray3[][] t2 = new TestArray3[2][3];
        for (int i = 0; i < t1.length; i++) {
            for (int j = 0; j < t1[i].length; j++) {
                t1[i][j] =new TestArray3();
            }
        }
        for(int i = 0 ;i<t1.length;i++){
            System.arraycopy(t1[i], 0, t2[i], 0, t1[i].length);
        }
        show2(t1);
        System.out.println("=======");
        show2(t2);
        t2[0][0].setA(1000);
        System.out.println("====改变后====");
        show2(t1);
        System.out.println("=======");
        show2(t2);
    }
}

（4）Arrays.copyof方法拷贝

基本类型

public class TestDemo7 {
    public static void show1(int[][] array){
        for(int i = 0;i<array.length;i++){
            for(int j = 0;j<array[i].length;j++){
                System.out.print(array[i][j]+" ");
            }
            System.out.println();
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[][] array = {{1,2,3},{4,5,6}};
        int[][] array2 = new int[2][3];
        array2 = Arrays.copyOf(array,array2.length);
        show1(array);
        System.out.println("=========");
        show1(array2);
        array2[0][0] = 1000;
        System.out.println("=====改变后哦====");
        show1(array);
        System.out.println("=========");
        show1(array2);
    }
}

引用类型

class TestArray4{
    private int a=10;
    public int getA() {
        return a;
    }
    public void setA(int a) {
        this.a = a;
    }
}
public class TestDemo7 {
    public static void show2(TestArray4[][] Array)
    {
        for (int i = 0; i < Array.length; i++) {
            for (int j = 0; j < Array[i].length; j++) {
                System.out.print(Array[i][j].getA()+"  ");
            }
            System.out.println();
        }
    }
    public static void main(String[] args) {
        TestArray4[][] t1 = new TestArray4[2][3];
        TestArray4[][] t2 = new TestArray4[2][3];
        for (int i = 0; i < t1.length; i++) {
            for (int j = 0; j < t1[i].length; j++) {
                t1[i][j] =new TestArray4();
            }
        }
        t2 = Arrays.copyOf(t1, t1.length);
        show2(t1);
        System.out.println("=========");
        show2(t2);
        System.out.println("=====改变后哦====");
        t2[0][0].setA(100);
        show2(t1);
        System.out.println("=========");
        show2(t2);
    }
}