Java 类型转换

Java 类型转换

• int转Integer

int int0 = 1;
Integer integer1 = int0; // 自动装箱
Integer integer2 = new Integer(int0);
Integer integer3 = Integer.valueOf(int0);

• Integer转int

Integer integer0 = 2;
int int1 = integer0; // 自动拆箱
int int2 = integer0.intValue(); // 返回int类型

• int转String

int int0 = 1;
String str1 = String.valueOf(int0);
str1 = Integer.valueOf(int0).toString(); // 先转为Integer

• String转int

String str0 = "3";
int int1 = Integer.parseInt(str0);

• Integer转String

Integer integer0 = 2;
String str1 = integer0.toString();

• String转Integer

String str0 = "3";
Integer integer1 = new Integer(str0);
Integer integer2 = Integer.valueOf(str0);

• int[]数组转Integer[]数组

int[] ints0 = new int[]{1, 2, 3};
Integer[] integers1 = Arrays.stream(ints0).boxed().toArray(Integer[]::new);

• Integer[]数组转int[]数组

Integer[] integers0 = new Integer[]{4, 5, 6};
int[] ints1 = Arrays.stream(integers0).mapToInt(Integer::intValue).toArray();

• int[]数组转List

int[] ints0 = new int[]{1, 2, 3};
List list1 = Arrays.stream(ints0).boxed().collect(Collectors.toList());

• List转int[]数组

List<Integer> list0 = new ArrayList<Integer>();		
list0.add(10);
list0.add(11);
list0.add(12);
int[] ints1 = Arrays.stream(list0.toArray(new Integer[0])).mapToInt(Integer::intValue).toArray();

• Integer[]转List

Integer[] integers0 = new Integer[]{4, 5, 6};
List list1 = Arrays.stream(integers0).collect(Collectors.toList());
List list2 = Arrays.asList(integers0);

• List转Integer[]

Integer[] integers0 = new Integer[]{4, 5, 6};
Integer[] integers1 = list0.toArray(new Integer[0]);

• String[]转List

String[] strs0 = new String[]{"7","8","9"};
List list1 = Arrays.asList(strs0);

• List转String[]

List<Integer> list0 = new ArrayList<Integer>();		
list0.add(10);
list0.add(11);
list0.add(12);
String[] strs1 = list0.toArray(new String[0]);