一、数据类型转换
1、基本数据类型的转换
// Kotlin
val a: Double = 5.0
val b: Int = a.toInt()
// Java
double a = 5.0;
int b = (int) a;
2、数组类型的转换
// Kotlin
val a: IntArray = intArrayOf(1, 2, 3)
val b: Array<Integer> = a.toTypedArray()
// Java
int[] a = new int[]{1, 2, 3};
Integer[] b = Arrays.stream(a).boxed().toArray(Integer[]::new);
二、空安全
1、判空语法的转换
// Kotlin
val a: String? = null
if (a == null) {
println("a is null")
}
// Java
String a = null;
if (a == null) {
System.out.println("a is null");
}
2、非空断言的转换
// Kotlin
val a: String? = null
val b = a!!
// Java
String a = null;
String b = Objects.requireNonNull(a, "a is null");
三、Lambda表达式
1、Lambda表达式的转换
// Kotlin
val list = listOf(1, 2, 3)
list.filter { it > 1 }.map { it * 2 }
// Java
List<Integer> list = Arrays.asList(1, 2, 3);
list.stream().filter(i -> i > 1).map(i -> i * 2).collect(Collectors.toList());
2、扩展函数的转换
// Kotlin
fun String.toTitleCase(): String {
return split(" ").joinToString(" ") { it.capitalize() }
}
// Java
public static String toTitleCase(String str) {
return Arrays.stream(str.split(" ")).map(s -> s.substring(0, 1).toUpperCase() + s.substring(1)).collect(Collectors.joining(" "));
}
四、DSL语法
1、DSL语法的转换
// Kotlin
class Person {
var name: String? = null
var age: Int? = null
}
fun person(block: Person.() -> Unit): Person {
val p = Person()
p.block()
return p
}
person {
name = "Alice"
age = 25
}
// Java
public class Person {
private String name;
private Integer age;
public Person name(String name) {
this.name = name;
return this;
}
public Person age(Integer age) {
this.age = age;
return this;
}
}
Person person = new Person()
.name("Alice")
.age(25);
2、Lambda参数的转换
// Kotlin
fun foo(block: (Int, String) -> Unit) {
block(42, "hello")
}
foo { a, b ->
println("a=$a, b=$b")
}
// Java
public void foo(BiConsumer<Integer, String> block) {
block.accept(42, "hello");
}
foo((a, b) -> System.out.println("a=" + a + ", b=" + b));
五、拓展函数
1、拓展函数的转换
// Kotlin
fun String.hasSpaces(): Boolean {
return find { it == ' ' } != null
}
// Java
public static boolean hasSpaces(String str) {
return str.contains(" ");
}
String str = "hello world";
hasSpaces(str);
2、Kotlin原生函数的转换
// Kotlin
val list = listOf(1, 2, 3)
list.forEachIndexed { index, value ->
println("index=$index, value=$value")
}
// Java
List<Integer> list = Arrays.asList(1, 2, 3);
IntStream.range(0, list.size()).forEach(i -> System.out.println("index=" + i + ", value=" + list.get(i)));
原创文章，作者：小蓝，如若转载，请注明出处：https://www.506064.com/n/254913.html
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