Java JDK 1.8 lambda的用法详解

Java JDK 1.8 lambda的用法详解

具体代码如下所示：

public class Student {

private String id;

private String name;

private String age;

private String address;

public Student(String id, String name, String age, String address) {

this.id = id;

this.name = name;

this.age = age;

this.address = address;

}

public String getId() {

return id;

}

public void setId(String id) {

this.id = id;

}

public http://String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getAge() {

return age;

}

public void setAge(String age) {

this.age = age;

}

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

@Override

public String toString() {

return "Student{" +

"id='" + id + '\'' +

", name='" + name + '\'' +

", age='" + age + '\'' +

", address='" + address + '\'' +

'}';

}

}

public class TestStrean {

public static void main(String[] args){

Student stuA = new Student("1", "A", "M", "184");

Student stuB = new Student("2", "B", "G", "163");

Student stuC = new Student("3", "C", "M", "175");

Student stuD = new Student("4", "D", "G", "158");

Student stuE = new Student("5", "E", "M", "175");

List list = new ArrayList<>();

list.add(stuA);

list.add(stuB);

list.add(stuC);

list.add(stuD);

list.add(stuE);

/*-----------forEach-----------------------*/

// list.forEach(item -> item.setId(item.getAddress()+"test") );

/*-----------filter-----------------------*/

// List newList=list.stream().filter(item -> item.getAge().contains("G")).collect(Collectors.toList());

/*-----------filter的复杂应用-----------------------*/

// list.stream().filter(new Predicate(){

//

// @Override

// public boolean test(Student student) {

// if(student.getName() !=null){

// return student.getName().contains("30");

// }else{

// return true;

// }

// }

// }).collect(Collectors.toList());

/*-----------分页-----------------------*/

// List newList=list.stream().skip(4).limit(3).collect(Collectors.toList());

/*-----------map 返回一个新的list

// List newList=list.stream().map(item ->{

// return new Student(

// item.getAddress(),

// item.getAge(),

// item.getName(),

// item.getId()

// );

// }).collect(Collectors.toList());

/*-----------map 返回一个原来的的list并赋值-----------------------*/

// List newList=list.stream().map(item ->{

// item.setId("1");

// return item;

// }).collect(Collectors.toList());

/*-----------flatMap-----------------------*/

// List newList= list.stream().flatMap(item ->{

// String[] split =item.getAddress().split("");

// String[] s2 = (String[]) Arrays.stream(split).filter(s -> s.contains("1")).toArray();

// return s2;

// });

/*-----------sorted compareTo排序-----------------------*/

// List newList=list.stream().sorted((o1,o2)->{

// if(o1.getAddress().equals(o2.getAddress())){

// return Integer.parseInt(o1.getId())-Integer.parseInt(o2.getId());

// }else{

// return o1.getAddress().compareTo(o2.getAddress());

// }

// }).collect(Collectors.toList());

/*-----------sorted Comparator排序-----------------------*/

// List newList=list.stream().sorted(

// Comparator.comparing(Student::getAddress).reversed()

// ).collect(Collectors.toList());

/*-----------sorted3 多条件排序-----------------------*/

// List newList=list.stream().sorted(

// Comparator.comparing(Student::getAddress).thenComparing(Comparator.comparing(Student::getId).reversed())

// ).collect(Collectors.toList());

// boolean b=list.stream().anyMatch(item -> item.getAge().contains("G"));

// System.out.println(b);

/*-----------Collector tomap----------------------*/

// Map newList=list.stream().sorted(

// Comparator.comparing(Student::getAddress).thenComparing(Comparator.comparing(Student::getId).reversed())

// ).collect(Collectors.toMap(Student::getId,Student::getAddress));

/*-----------Collector groupingBy----------------------*/

Map> ageMap = list.stream().collect(Collectors.groupingBy(Student::getAddress));

System.out.println(ageMap );

}

}

知识点扩展：

jdk 1.8 Lambda 表达式 遍历数组

Lambda 表达式可以把回调函数作为参数传递

常用的遍历数组的方式如下

List datas = new ArrayList<>();

//遍历

datas.forEach(item->{

System.out.println(item);

});

说明：

item就是每次遍历的当前元素

总结

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