java从入门到精通习题

public class Eval { // 新建类

public static void main(String[] args) { // 主方法

String regex = "1[35]\\d{9}";

Stringtext="150****0000";

if (text.matches(regex)) {

System.out.println(text + "是合法的手机号");

}

}

}

5.4

public class Eval { // 新建类

public static void main(String[] args) { // 主方法

StringBuilder builder = new StringBuilder("a");

for (int i = 1; i <= 10; i++) {

builder.append(i);

}

System.out.println(builder.toString());

}

}

6.1

import java.util.*;

public class Eval { // 创建类

public static void main(String [] args)

{

int arr1[]=new int[]{1,2,3,4,5};

int arr2[] = Arrays.copyOf(arr1, 3);

// 复制源数组中从下标0开始的3个元素到目的数组，从下标0的位置开始存储。

for(int i=0;i

System.out.print(arr1[i]);

System.out.println();

for(int j=0;j

System.out.print(arr2[j]);

System.out.println();

}

}

import java.util.*;

public class Eval { // 创建类

public static void main(String[] args) {

int arr[] = new int[] { 10, 2, 3, 4, 5, 6, 7, 8, 9 };

Arrays.sort(arr);

System.out.println(arr[0]);

}

}

6.3

import java.util.*;

public class Text { // 创建类

public static void main(String[] args) {

String arr[] = new String[] { "ac", "bc", "dc", "yc" };

System.out.println("替换前：");

for (String str : arr) {

System.out.print(str+"\t");

}

Arrays.fill(arr, 2, 3, "bb");

System.out.println("\n替换后：");

for (String str2 : arr) {

System.out.print(str2+"\t");

}

}

}

6.4

public class Eval { // 创建类

public static void main(String[] args) {

int arr[][]=new int[][]{{1,2,3},{4,5,6},{7,8,9}};

System.out.println("数组原有内容：");

for(int i = 0;i

for(int j=0;j

System.out.print(arr[i][j]);

}

System.out.println();

}

System.out.println("行列互换后数组内容：");

for(int i = 0;i

for(int j=0;j

System.out.print(arr[j][i]);

}

System.out.println();

}

}

7.1

package com.lzw;

public class UseCase1 {

private String name;

public String getName() {

return name;

}

public void setName(String name) {

= name;

}

}

//另一个java文件

package com.lzw;

public class UseCase2 extends UseCase1{

public static void main(String[] args) {

UseCase1 u=new UseCase1();

u.setName("123");

System.out.println(u.getName());

}

}

7.2

package com.lzw;

public class UseCase3 {

private float height;

private float width;

public UseCase3(float height,float width){ this.height=height;

this.width=width;

}

public float square(){

return height*width;

}

public static void main(String args[]){

UseCase3 u=new UseCase3(3.5f,4.5f);

System.out.println(u.square());

}

}