集合複習list to map
阿新 • • 發佈:2018-11-10
package listtomap; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Set; public class listtomap { public static void main(String[] args) { // TODO Auto-generated method stub Map<Integer,String> map=listtomap(); Set<Entry<Integer,String>> entryset=map.entrySet(); Iterator<Entry<Integer,String>> it=entryset.iterator(); while(it.hasNext()) { Entry<Integer,String> entry=it.next(); System.out.println(entry); } } public static Map<Integer,String> listtomap() { Student stu1=new Student(1,"zhangsan",22); Student stu2=new Student(2,"lisi",24); Student stu3=new Student(3,"zhaowu",23); Student stu4=new Student(4,"wanba",22); List<Student> list=new ArrayList<>(); list.add(stu1); list.add(stu2); list.add(stu3); list.add(stu4); for(int i=0;i<list.size();i++) { System.out.println(list.get(i)); } System.out.println(list); Map<Integer,String> map=new HashMap<Integer,String>(); for(Student st:list) { map.put(st.getSno(),st.getName()); } return map; } }
Student 類:
package listtomap; public class Student implements Comparable<Student>{ private int sno; private String name; private int age; public Student(int sno, String name, int age) { super(); this.sno = sno; this.name = name; this.age = age; } @Override public String toString() { return "Student [sno=" + sno + ", name=" + name + ", age=" + age + "]"; } public int getSno() { return sno; } public void setSno(int sno) { this.sno = sno; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public static void main(String[] args) { // TODO Auto-generated method stub } @Override public int compareTo(Student arg0) { // TODO Auto-generated method stub if(this.age==arg0.age) { return this.sno-arg0.sno; }else { return this.age-arg0.age; } } }