List集合的四种遍历方式
为了便于理解，直接上代码，首先定义一个学生类，手动创建四个学生对象，并添加到list集合中：

public class TestList {
public static void main(String[] args) {
List studentList = new ArrayList();
Student s1 = new Student("zhangsan", 31);
Student s2 = new Student("lisi", 32);
Student s3 = new Student("wangwu", 33);
Student s4 = new Student("zhaoliu", 34);
studentList.add(s1);
studentList.add(s2);
studentList.add(s3);
studentList.add(s4);
}
}
class Student {
String name;
int age;

public Student() {
super();
}

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

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;
}

}
1、普通for循环.
public class TestList {
public static void main(String[] args) {
List studentList = new ArrayList();
Student s1 = new Student("zhangsan", 31);
Student s2 = new Student("lisi", 32);
Student s3 = new Student("wangwu", 33);
Student s4 = new Student("zhaoliu", 34);
studentList.add(s1);
studentList.add(s2);
studentList.add(s3);
studentList.add(s4);

for (int i = 0; i < studentList.size(); i++) {
Student s = (Student) studentList.get(i);
System.out.println(s.getName());
System.out.println(s.getAge());
}
}
}
2、增强for循环（较多使用，建议掌握）：可以使用在遍历list集合、set集合和数组中.
public class TestList {
public static void main(String[] args) {
List studentList = new ArrayList();
Student s1 = new Student("zhangsan", 31);
Student s2 = new Student("lisi", 32);
Student s3 = new Student("wangwu", 33);
Student s4 = new Student("zhaoliu", 34);
studentList.add(s1);
studentList.add(s2);
studentList.add(s3);
studentList.add(s4);

//格式：for(对象类型 对象: 集合) ,其中对象类型建议使用泛型集合。
for(Object os : studentList){
    Student s = (Student) os;
System.out.println(s.getName());
System.out.println(s.getAge());
}
}
}
3、迭代器循环, js中没有.
public class TestList {
public static void main(String[] args) {
List studentList = new ArrayList();
Student s1 = new Student("zhangsan", 31);
Student s2 = new Student("lisi", 32);
Student s3 = new Student("wangwu", 33);
Student s4 = new Student("zhaoliu", 34);
studentList.add(s1);
studentList.add(s2);
studentList.add(s3);
studentList.add(s4);

//先创建一个List集合的迭代器，然后从中取集合对象。
Iterator it = studentList.iterator();
//it.hasNext()判断迭代器中有无下一个元素。
while(it.hasNext()){
Object os = it.next();
Student s = (Student) os;
System.out.println(s.getName());
System.out.println(s.getAge());
}
}
}
4、使用JDK1.8后的新技术，lambda表达式（个人认为最简单）.
public class TestList {
public static void main(String[] args) {
List studentList = new ArrayList();
Student s1 = new Student("zhangsan", 31);
Student s2 = new Student("lisi", 32);
Student s3 = new Student("wangwu", 33);
Student s4 = new Student("zhaoliu", 34);
studentList.add(s1);
studentList.add(s2);
studentList.add(s3);
studentList.add(s4);

//forEach( (参数（可多个）)->{ 循环体 } )
studentList.forEach((os) -> {
Student s = (Student) os;
System.out.println(s.getName());
System.out.println(s.getAge());
});
}
}