java常見的类型转换

java常见的类型转换总结

(1) String -> int

String str1 = "123";
int value = Integer.valueOf(str1);

String str1 = "123";
int value2 = Integer.parseInt(str1);

( 2) int -> String

int value = 123;
String str1 = String.valueOf(value);

int value = 123;
String str2 =Integer.toString(value);

(3) Integer -> String

//方法一:Integer类的静态方法toString()
Integer a = 2;
String str = Integer.toString(a)
    
//方法二:Integer类的成员方法toString()
Integer a = 2;
String str = a.toString();

//方法三:String类的静态方法valueOf()
Integer a = 2;
String str = String.valueOf(a);

(4) String -> Integer

String str = "123";
Integer value = Integer.valueOf(str);
Integer value2 = Integer.parseInt(str);

(5) int -> Integer

int a = 123;
Integer value = new Integer(a);
Integer value2 = Integer.valueOf(a);

(6) Integer -> int

Integer a = 123;
int value = a.intValue();

(7) String -> float

String str = "123";
float value = Float.valueOf(str);
float value2 = Float.parseFloat(str);

(8) float -> String

float a = 123.0f;
String str = String.valueOf(a);
String str2 = Float.toString(a);

(9) Float -> String

Float a = 123f;
String str1 = a.toString();
String str2 = String.valueOf(a);
String str3 = a.toString();

(10) String -> Float

String str = "123";
Float value = Float.valueOf(str);
Float value2 = Float.parseFloat(str);

(11) String ->double String ->long 同理 其他类型转换同理

（12）String -> char

String str = "yangxu";
char c = str.charAt(1);

(13) char -> String

char c = 'c';
String str = String.valueOf(c);
String str2 = Character.toString(c);
String str3 = new Character(c).toString();
String str4 = new String(new char[]{'c'});

(14) char[ ] -> String

char [] c = new char[]{'a','b','c'};
String str =String.copyValueOf(c);

(15) String -> char[ ]

String str = "yangxu";
char[] arr= str.toCharArray();

(16) Interger[ ] -> int[ ]

Integer[] arr = new Integer[]{1,2,3,4,5,6,76};
int[] arrs = Arrays.stream(arr).mapToInt(Integer::valueOf).toArray();

(17) int[ ] -> Integer[ ]

int[] a={1,3,4};
Integer[] arr= IntStream.of(a).boxed().collect(Collectors.toList()).toArray(new Integer[0]);

Integer[] integers = Arrays.stream(a).boxed().toArray(Integer[]::new);

(18) List -> int[ ]

List< Integer > list = new ArrayList<>();
list.add(165);
list.add(25);
list.add(24);
list.add(23);
int[] int1 = list.stream().mapToInt(Integer::valueOf).toArray();
int[] int2 = list.stream().mapToInt(Integer::intValue).toArray();

(19) int[ ] -> List

int[] arr = {1,2,3,4,45};
List list = Arrays.stream(arr).boxed().collect(Collectors.toList());

(20) Integer[ ] -> List

Integer[] arr= {23,12,14};
List<Integer> list=Arrays.asList(arr);
List<Integer> list1 = new ArrayList<>(Arrays.asList(arr));

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