CPT204 Lab 代码

Scabbards_2024-04-02 23:43

Lab1 OOP Review 1

1.1

java 复制代码 
package Lab1;

import java.util.Arrays;
import java.util.Scanner;

public class ex11 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int length = 5;
        double[] test1 =new double[length];
        System.out.println("the length of input is"+length);
        for (int i = 0; i < 5; i++) {
            test1[i] = sc.nextDouble();
        }
        reverseInPlace(test1);
        System.out.println(Arrays.toString(test1));

    }
    public static void reverseInPlace(double[] arr){
        for (int i = 0; i < arr.length/2; i++) {
            double temp = arr[i];
            arr[i] = arr[arr.length-1-i];
            arr[arr.length-1-i] = temp;
        }
    }
}

1.2

java 复制代码 
package Lab1;

import java.util.Arrays;
import java.util.Scanner;

public class ex12 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int length = 5;
        int[] test =new int[length];
        System.out.println("the length of input is"+length);
        for (int i = 0; i < 5; i++) {
            test[i] = sc.nextInt();
        }
        if (isConsecutiveFour(test)){
            System.out.println(Arrays.toString(test));
        }else {
            System.out.println("no");
        }
    }
    

    public static boolean isConsecutiveFour(int[] values){
        for (int i = 0; i < values.length-3; i++) {
            if (values[i] == values[i + 1] && values[i] == values[i + 2] && values[i] == values[i + 3]){
                return true;
            }
        }
        return false;
    }
}

1.3

java 复制代码 
package Lab1;

public class ex13_StopWatch {
    long startTime;
    long endTime;

    public ex13_StopWatch(){
        this.startTime= System.currentTimeMillis();
        this.endTime= System.currentTimeMillis();
    }

    public ex13_StopWatch(int startTime, int endTime) {
        this.startTime = startTime;
        this.endTime = endTime;
    }

    public void start(){
        this.startTime = System.currentTimeMillis();
    }

    public void end(){
        this.endTime = System.currentTimeMillis();
    }

    public long getElapsedTime(){
        return this.endTime- this.startTime;
    }


}

1.4

太常见了就不写了

Lab2 OOP Review 2

Lab3 Abstract Classes and Interfaces

3.1

java 复制代码 
package Lab3;

import java.util.ArrayList;

public class ex31 {
    public static void main(String[] args) {
        ArrayList<Number> arr = new ArrayList<>();
        arr.add(1);
        arr.add(2);
        arr.add(3);
        arr.add(4);
        shuffle(arr);
        System.out.println(arr.toString());

    }

    public static void shuffle(ArrayList<Number> list){
        for (int i = 0; i < list.size(); i++) {
            int index =  (int) (Math.random()*list.size());
            Number temp =  list.get(i);
            list.set(i, list.get(index));
            list.set(index,temp);
        }
    }

}

3.2

java 复制代码 
package Lab3;

public class ex32 {
    public static void main(String[] args) {
        ComparableCircle c1 = new ComparableCircle(2);
        ComparableCircle c2 = new ComparableCircle(4);
        ComparableCircle ans = Max.max(c1, c2);
        System.out.println(ans.getradius());
    }
}

class Circle {
    private double radius;

    public Circle(double radius){
        this.radius = radius;
    }

    public double getradius(){
        return radius;
    }
}

class ComparableCircle extends Circle implements Comparable{
    public ComparableCircle(double radius){
        super(radius);
    }

    @Override
    public int compareTo(ComparableCircle c) {
        if (getradius() > c.getradius()){
            return 1;
        }
        else if (getradius() < c.getradius()){
            return -1;
        }
        else{
            return 0;
        }
    }
}


interface Comparable {
    public abstract int compareTo(ComparableCircle c);
}

class Max{
    public static ComparableCircle max(ComparableCircle c1, ComparableCircle c2){
        if (c1.compareTo(c2)>=0){
            return c1;
        }
        else return c2;
    }
}

3.3

3.4

接口中的字段必须是常量（即 static final），而不是实例字段。因此，String name; 应该改为 String NAME = "Animal"; 或者直接在类中使用 String getName(); 方法来获取名称。

java 复制代码 
public interface ex34_Animal {
    String NAME = "Animal"; // 常量
    void makesound(); // 抽象方法
}

接口中不能包含具有实现的方法。接口中的方法默认是抽象的，即没有具体的实现。

在Java中，抽象类是不能被直接实例化的，即不能使用 new 关键字来创建抽象类的对象。因此，当你尝试在 main 方法中实例化 ex34_Myclass 类的对象时，会导致编译错误。

Lab4 Generics

4.1

java 复制代码 
package Lab4;

import java.util.ArrayList;

public class ex41 {
    public static void main(String[] args) {
        ArrayList<Number> arr = new ArrayList<>();
        arr.add(1);
        arr.add(2);
        arr.add(3);
        arr.add(4);
        shuffle(arr);
        System.out.println(arr.toString());
    }

    public static <E> void shuffle(ArrayList<E> list){
        for (int i = 0; i < list.size(); i++) {
            int index =  (int) (Math.random()*list.size());
            E temp =  list.get(i);
            list.set(i, list.get(index));
            list.set(index,temp);
        }
    }


}

4.2

java 复制代码 
package Lab4;

import java.util.ArrayList;

//这个地方卡了半天属于是没有看清楚要求，之前弄成ArrayList<Number>了，然后compareable里面估计就没办法兼容了
public class ex42 {
    public static void main(String[] args) {
        ArrayList<Integer> arr = new ArrayList<>();
        arr.add(1);
        arr.add(2);
        arr.add(3);
        arr.add(4);
        Number maxnum = ex42.<Integer>max(arr);
        System.out.println(maxnum);
    }

    public static <E extends Comparable<E>> E max(ArrayList<E> list){
        E larger = list.get(0);
        for (int i = 0; i < list.size(); i++) {
            if (list.get(i).compareTo(larger)>0){
                larger = list.get(i);
            }
        }
        return larger;
    }

}

4.3

java 复制代码 
public class ex43 {
    public class  pair <E,F>{
        public E first;
        public F second;

        public pair(E e, F i) {
        }
    }

    pair<String,Integer> p1 = new pair<>("hello",1);
}

4.4

java 复制代码 
package Lab4;

import java.util.ArrayList;
import java.util.Arrays;

public class ex44 {
    public static void main(String[] args) {
        ArrayList<Integer> c = new ArrayList<>();
        c.add(3);
        c.add(4);
        print(c); //这里报红是因为泛型没有继承性
    }

    public static void print(ArrayList<? extends Object> o){ //所以要用泛型的通配符解决这个问题
        for (Object e : o){
            System.out.println(e);
        }
    }
}

Lab5 Lists, Stacks, Queues, and Priority Queues

5.1

java 复制代码 
package Lab5;

import java.util.Iterator;
import java.util.LinkedList;

public class ex51 {
    public static void main(String[] args) {
        LinkedList<Integer> ll = new LinkedList<>();
        int num = 100000;
        for (int i = 0; i < num; i++) {
            ll.add(i);
        }
        long starttimer = System.currentTimeMillis();

//        //i 遍历
//        for (int i = 0; i < num; i++) {
//            ll.get(i);
//        }

        //iterator遍历
        for (Integer i : ll) {
            System.out.println(" ");
        }

        long stoptimer = System.currentTimeMillis();

        System.out.println("time" + (stoptimer - starttimer));
    }


}

5.2

java 复制代码 
package Lab5;

import java.util.Arrays;
import java.util.PriorityQueue;

public class ex52 {
    public static void main(String[] args) {
        PriorityQueue<String> queue1 = new PriorityQueue<String>(Arrays.asList(
                new String[] {"George","Jim","John", "Blake", "Kevin", "Michael"}
        ));

        PriorityQueue<String> queue2 = new PriorityQueue<String>(Arrays.asList(
                new String[] {"George","Katie","Kevin", "Michelle", "Ryan"}
        ));

        //union
        System.out.println("The union of the two priority queues is "+queue1);

        // difference
        queue1.removeAll(queue2);
        System.out.println("The difference of the two priority queues is "+queue1);

        //intersection
        queue1.retainAll(queue2);
        System.out.println("The intersection of the two priority queues is "+queue1);

    }


}

5.3

java 复制代码 
package Lab5;

import java.util.Arrays;
import java.util.PriorityQueue;
import java.util.Stack;

//查看是否有成组的符号对
public class ex53 {
    public static void main(String[] args) {
        String str1 = "(int) ("0.1")";
        String str2 = "public void static main(String[] args){";
        System.out.println(checkpairs(str1));
        System.out.println(checkpairs(str2));

    }

    public static boolean checkpairs(String str){
        Stack<Character> s = new Stack<>();
        int length = str.length();
        boolean checkans = false;
        for (int i = 0; i < length; i++) {
            Character c = str.charAt(i);
            if(c=='{' || c=='['||c=='('){
                s.push(c);
            }
            else if(c=='}' || c==']'||c==')'){
                checkidentity(s,c);
            }
        }
        if (s.isEmpty()){
            checkans = true;
        }
        return checkans;
    }

    public static void checkidentity(Stack<Character>s, char c){
        char lastc = s.peek();
        if (ispair(lastc,c)){
            s.pop();
        }
        else {
            s.push(c);
        }
    }

    public static boolean ispair(char c1, char c2){
            return c1 == '{' && c2 == '}' || c1 == '[' && c2 == ']'|| c1 == '(' && c2 == ')';
    }


}
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