在Java 8中stream().map()，您可以将对象转换为其他对象
1.大写字符串列表
package .java8;
import ;
import ;
import ;
import ;
public class TestJava8 {
public static void main(String[] args) {
List<String> alpha = ("a", "b", "c", "d");
//Before Java8
List<String> alphaUpper = new ArrayList<>();
for (String s : alpha) {
(());
}
(alpha); //[a, b, c, d]
(alphaUpper); //[A, B, C, D]
// Java 8
List<String> collect = ().map(String::toUpperCase).collect(());
(collect); //[A, B, C, D]
// Extra, streams apply to any data type.
List<Integer> num = (1,2,3,4,5);
List<Integer> collect1 = ().map(n -> n * 2).collect(());
(collect1); //[2, 4, 6, 8, 10]
}
}2.对象列表 - >字符串列表
package .java8;
import ;
public class Staff {
private String name;
private int age;
private BigDecimal salary;
//...
}
package .java8;
import ;
import ;
import ;
import ;
import ;
public class TestJava8 {
public static void main(String[] args) {
List<Staff> staff = (
new Staff("mkyong", 30, new BigDecimal(10000)),
new Staff("jack", 27, new BigDecimal(20000)),
new Staff("lawrence", 33, new BigDecimal(30000))
);
//Before Java 8
List<String> result = new ArrayList<>();
for (Staff x : staff) {
(());
}
(result); //[mkyong, jack, lawrence]
//Java 8
List<String> collect = ().map(x -> ()).collect(());
(collect); //[mkyong, jack, lawrence]
}
}
对象列表 - >其他对象列表
3.1此示例说明如何将staff对象列表转换为对象列表StaffPublic。
package .java8;
import ;
public class Staff {
private String name;
private int age;
private BigDecimal salary;
//...
}
package .java8;
public class StaffPublic {
private String name;
private int age;
private String extra;
//...
}
3.2 Java 8之前。
package .java8;
import ;
import ;
import ;
import ;
public class BeforeJava8 {
public static void main(String[] args) {
List<Staff> staff = (
new Staff("mkyong", 30, new BigDecimal(10000)),
new Staff("jack", 27, new BigDecimal(20000)),
new Staff("lawrence", 33, new BigDecimal(30000))
);
List<StaffPublic> result = convertToStaffPublic(staff);
(result);
}
private static List<StaffPublic> convertToStaffPublic(List<Staff> staff) {
List<StaffPublic> result = new ArrayList<>();
for (Staff temp : staff) {
StaffPublic obj = new StaffPublic();
(());
(());
if ("mkyong".equals(())) {
("this field is for mkyong only!");
}
(obj);
}
return result;
}
}Java 8的例子
package .java8;
package .java8;
import ;
import ;
import ;
import ;
public class NowJava8 {
public static void main(String[] args) {
List<Staff> staff = (
new Staff("mkyong", 30, new BigDecimal(10000)),
new Staff("jack", 27, new BigDecimal(20000)),
new Staff("lawrence", 33, new BigDecimal(30000))
);
// convert inside the map() method directly.
List<StaffPublic> result = ().map(temp -> {
StaffPublic obj = new StaffPublic();
(());
(());
if ("mkyong".equals(())) {
("this field is for mkyong only!");
}
return obj;
}).collect(());
(result);
}
}
[
StaffPublic{name='mkyong', age=30, extra='this field is for mkyong only!'},
StaffPublic{name='jack', age=27, extra='null'},
StaffPublic{name='lawrence', age=33, extra='null'}
]