ListIterator

package heima;
import java.util.ArrayList;
import java.util.List;
import java.util.ListIterator;

public class kkk {

public static void main(String[] args) {
    List<String> list = new ArrayList<>();

list.add("hello");
list.add("world");
list.add("java");

    ListIterator<String>lit=list.listIterator();

while(lit.hasNext()){

String s= lit.next();
System.out.println(s);

}

}

}
package heima;

import java.util.ArrayList;
import java.util.List;
import java.util.ListIterator;

public class kkk {

public static void main(String[] args) {
    List<String> list = new ArrayList<>();
    list.add("hello");
    list.add("world");
    list.add("java");

// ListIterator lit = list.listIterator();
// while (lit.hasNext()) {
// String s = lit.next();
// System.out.println(s);
// }
// System.out.println("------------");
// while(lit.hasPrevious()){
// String s= lit.previous();
// System.out.println(s);
// }
ListIteratorlit= list.listIterator();

    while(lit.hasNext()){
        String s=lit.next();
        if(s.equals("world")){
            lit.add("javaee");
        }

    }
    System.out.println(list);

}

}

package heima;

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

public class kkk {

public static void main(String[] args) {
    int[] arr={1,2,3,4,5};
    for(int i: arr){
        System.out.println(i);
    }
    System.out.println("--------");
String[] strArray={"hello","world","java"};
    for(String s:strArray){
        System.out.println(s);
    }
    System.out.println("-----------");
    List<String>list=new ArrayList<String>();
    list.add("hello");
    list.add("world");
    list.add("java");
    for(String s: list){
        System.out.println(s);
    }
    System.out.println("---------");

for(String s:list){

if(s.equals("world")){
    list.add("javaee");
}

}

}

}
//1
// 2
// 3
// 4
// 5
// --------
// hello
// world
// java
// -----------
// hello
// world
// java
// ---------
// Exception in thread "main" java.util.ConcurrentModificationException
// at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:911)
// at java.util.ArrayList$Itr.next(ArrayList.java:861)
// at heima.kkk.main(kkk.java:26)
//
// 进程已结束，退出代码为 1

package heima;

public class Student {

private String name;
private int age;

public Student(String name, int age) {
    this.name = name;
    this.age = age;
}

public Student(String name) {
    this.name = name;
}

public Student(int age) {
    this.age = age;
}

public Student() {
}

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;
}

}
package heima;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ListDemo {

public static void main(String[] args) {
    List<Student>list=new ArrayList<>();
    Student s1=new Student("ddwe",55);
    Student s2=new Student("dd",52);
    Student s3=new Student("add",77);
    list.add(s1);
    list.add(s2);
    list.add(s3);
    Iterator<Student>it=list.iterator();
    while(it.hasNext()){
        Student s= it.next();
        System.out.println(s.getName()+s.getAge());
    }

for(int i=0;i< list.size();i++){

Student s=list.get(i);
System.out.println(s.getName()+s.getAge());

}
for(Student s:list){

System.out.println(s.getName()+s.getAge());

}

}

}