数据结构LIst

某校科技有若干个学生，（学生对象放在一个LIst当中），每个学生有一个姓名，班级和某次考试成绩的属性（double），某次考试结束后，每个学生都获得了一个考试成绩。遍历LIst集合，并把学生对象的属性打印出来

import java.util.ArrayList;

class Student {
    private String name;
    private String classes;
    private double score;

    public Student(String name, String classes, double score) {
        this.name = name;
        this.classes = classes;
        this.score = score;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + ''' +
                ", classes='" + classes + ''' +
                ", score=" + score +
                '}';
    }
}
public class Main {
    public static void main(String[] args) {
        ArrayList students = new ArrayList<>();
        students.add(new Student("gaobo", "102", 18.3));
        students.add(new Student("gaobo1", "102", 128.3));
        students.add(new Student("gaobo1", "102", 138.3));
        System.out.println(students);
    }
}

分析代码可以知道，ArrayList中存放的是Student这个对象，所以每次添加的时候都要new一个新的学生对象。

有一个List当中存放的是整型数据，要求使用Collection.sort进行排序

import java.util.ArrayList;
import java.util.Collections;

public class Main {
    public static void main(String[] args) {
        ArrayList integers = new ArrayList<>();
        integers.add(22);
        integers.add(2);
        integers.add(33);
        Collections.sort(integers);
        System.out.println(integers);
    }
}

这题int型就放int对应的类，直接调用Collection方法下面的sort类就行了

删除第一个字符串当中出现的第二个字符串中的字符

String str1 = “welcome to bit”;

String str2 = “come”;

输出结果：

wl t bit

用String解决

import java.util.Scanner;
public class Main {
    public static String fun(String str1, String str2) {
        StringBuilder sb = new StringBuilder();
        for(int i = 0; i < str1.length(); i ++) {
            char ch = str1.charAt(i);
            if(! str2.contains(ch+"")) {
                sb.append(ch);
            }
        }
        return sb.toString();
    }
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str1 = scanner.nextLine();
        String str2 = scanner.nextLine();
        System.out.println(fun(str1, str2));
    }
}

用ArrayList解决

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        String str1 = "welcome to bit";
        String str2 = "come";
        ArrayList list = new ArrayList<>();
        for(int i = 0; i < str1.length(); i ++) {
            char ch = str1.charAt(i);
            if(! str2.contains(ch+"")) {
                list.add(ch);
            }
        }
        for(char ch : list) {
            System.out.print(ch);
        }
    }
}

打印一幅扑克牌

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

class Card {
    private String name;
    private int rank;

    public Card(String name, int rank) {
        this.name = name;
        this.rank = rank;
    }

    @Override
    public String toString() {
        return "[ " + this.name + " " + this.rank + " ]";
    }
}
public class Main {
    public static List buyCard() {
        String[] suits = {"♥", "♠", "♦", "♣"};
        ArrayList cards = new ArrayList<>();
        for(int i = 0; i < 4; i ++) {
            for(int j = 1; j <= 13; j ++) {
                cards.add(new Card(suits[i], j));
            }
        }
        return cards;
    }
    public static void swap(List cards, int i, int j) {
        Card tmp = cards.get(i);
        cards.set(i, cards.get(j));
        cards.set(j, tmp);
    }
    public static void buffCard(List cards) {
        int size = cards.size();
        for(int i = size - 1; i > 0; i --) {
            Random random = new Random();
            int ran = random.nextInt(i);
            swap(cards, i, ran);
        }
    }
    public static void main(String[] args) {
        List cards = buyCard();
        System.out.println("买牌" + cards);
        buffCard(cards);
        System.out.println("洗牌" + cards);
        ArrayList> hand = new ArrayList<>();
        ArrayList hand1 = new ArrayList<>();
        ArrayList hand2 = new ArrayList<>();
        ArrayList hand3 = new ArrayList<>();
        hand.add(hand1);
        hand.add(hand2);
        hand.add(hand3);
        for(int i = 0; i < 5; i ++) {
            for(int j = 0; j < 3; j ++) {
                hand.get(j).add(cards.remove(0));
            }
        }
        System.out.println("第一个人的牌：" + hand1);
        System.out.println("第二个人的牌：" + hand2);
        System.out.println("第三个人的牌：" + hand3);
        System.out.println("剩下的牌：" + cards);
    }
}