Map接口(一種成對存儲的關係)
鍵(key)-值(value)對。Map類中存儲的“鍵值對”通過鍵來標識,所以“鍵對象”不可重複(如果鍵對象重複,則新的”鍵值對“覆蓋舊的”鍵值對“)
Map接口常用方法(1)
Map<Integer,String> m1 = new HashMap<>();
Map<Integer,String> m2 = new HashMap<>();
1、m1.put(1,"one") //存放鍵值對
2、m1.get(1) //通過鍵對象找到值對象
3、m1.remove(1) //通過鍵對象刪除對應的鍵值對
4、m1.size() //返回m1容器中鍵值對的數量
5、m1.isEmpty() //Map容器是否爲空
6、m1.clear() //清空Map容器內所有鍵值對
7、m1.containsKey(1) //容器中是否包含了1這個鍵對象對應的鍵值對
8、m1.containsValue("one") //容器中是否包含了”one“這個值對象對應的鍵值對
9、m1.putAll(m2) //將容器2中所有鍵值對加入到容器1中
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Map接口常用方法(2)
public class 日常 {
public static void main(final String[] args) {
Employee e1 = new Employee(1001,"王爍",20000);
Employee e2 = new Employee(1002,"王小爍",40000);
Map<Integer,Employee> map = new HashMap<>();
map.put(1,e1);
map.put(2,e2);
System.out.println(map.get(1));
System.out.println(map.get(2));
}
}
class Employee{ //創建一個僱員對象
private int id;
private String ename;
private double salary;
public Employee(int id, String ename, double salary) { //構造器
super();
this.id = id;
this.ename = ename;
this.salary = salary;
}
public String toString() { //重寫
return "id:"+id+" name:"+ename+" 薪水:"+salary;
}
public int getId() { //使用set、get
return id;
}
public void setId(int id) {
this.id = id;
}
public String getEname() {
return ename;
}
public void setEname(String ename) {
this.ename = ename;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
}
運行結果:
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