Java中List集合的四种常见遍历方法

秒速五厘米 2022-12-20 08:41 175阅读 0赞

## 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. ##

## 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）. ##