ArrayList
ArrayList 实现增删改查
package test; import java.util.ArrayList; import java.util.Iterator; /** * @Author: Mo * @Date: 2020/12/6 11:11 */ public class list { ArrayList<String > list1=new ArrayList<String>(); public ArrayList<String> addMethod(){ list1.add("早饭"); list1.add("午饭"); list1.add("晚饭"); return list1; } public ArrayList<String> deleteMethod(){ list1.remove("早饭"); return list1; } public ArrayList<String> updateMethod(){ list1.set(0,"午饭多吃"); return list1; } public void selectMethod1(){ Iterator<String> it=list1.iterator(); while(it.hasNext()) { String string=it.next(); System.out.print(string+"\t"); } } public void selectMethod2(){ for(String s:list1){ System.out.print(s+"\t"); } } public void selectMethod3(){ for (int i = 0; i < list1.size(); i++) { System.out.print(list1.get(i)+"\t"); } } public static void main(String[] args) { list list1=new list(); System.out.println("赖床的三餐变化:"); list1.addMethod(); list1.selectMethod1(); System.out.println(); list1.deleteMethod(); list1.selectMethod2(); System.out.println(); list1.updateMethod(); list1.selectMethod3(); } }
HashSet
HashSet 实现增删改查
package test; import java.util.HashSet; import java.util.Iterator; /** * @Author: Mo * @Date: 2020/12/6 11:11 */ public class set { HashSet<String > set1=new HashSet<String>(); public HashSet<String> addMethod(){ set1.add("早饭"); set1.add("午饭"); set1.add("晚饭"); return set1; } public HashSet<String> deleteMethod(){ set1.remove("早饭"); return set1; } public HashSet<String> updateMethod(){ set1.remove("午饭"); set1.add("午饭多吃"); return set1; } //迭代器遍历 public void selectMethod(){ Iterator<String> it=set1.iterator(); while(it.hasNext()) { String string=it.next(); System.out.print(string+"\t"); } } /* foreach方法 遍历 public void selectMethod(){ for(String s:set1){ System.out.print(s+"\t"); } } */ public static void main(String[] args) { set set1=new set(); System.out.println("赖床的三餐变化:"); set1.addMethod(); set1.selectMethod(); System.out.println(); set1.deleteMethod(); set1.selectMethod(); System.out.println(); set1.updateMethod(); set1.selectMethod(); } }
HashMap
HashMap 实现增删改查
package test; import java.util.HashMap; import java.util.Iterator; import java.util.Map; /** * @Author: hyy * @Date: 2020/12/6 15:02 */ public class map { Map<String,String> map=new HashMap<String,String>(); public Map<String,String> addMethod(){ map.put("001","早饭"); map.put("002","午饭"); map.put("003","晚饭"); return map; } public Map<String,String> deleteMethod(){ map.remove("001"); return map; } public Map<String,String> updateMethod(){ map.remove("002"); map.put("001","多吃午饭"); return map; } /** 迭代器 遍历 */ public void selectMethod(){ Iterator <String> it=map.keySet().iterator(); while(it.hasNext()) { String s1=it.next(); String name=map.get(s1); System.out.println(s1+"\t"+name); } } public void selectMethod1(){ /** foreach()方法 遍历 * Map类提供了一个称为entrySet()的方法, * 这个方法返回一个Map.Entry实例化后的对象集 */ for (Map.Entry<String, String> entry : map.entrySet()){ System.out.println(entry.getKey() + "\t" + entry.getValue()); } } public static void main(String[] args) { map map1=new map(); map1.addMethod(); System.out.println(); map1.selectMethod(); System.out.println(); map1.deleteMethod(); System.out.println(); map1.selectMethod(); System.out.println(); map1.updateMethod(); System.out.println(); map1.selectMethod1(); } }