Java Overview
Table of Contents
1. Java Overview
1.1. 风格
class Util { int mX; int mData; static int sValue; public void helloWorld() { } }
1.2. 变量
- int x=10;
1.3. 函数
- int test(int a, int b) {}
1.4. 输入输出
1.5. 类型及转换
1.5.1. 基本类型
- boolean, byte, char, int, long, float, double
- array: int [] x={1,2,3}; int [] x=new int[]{1,2,3}; int [] x=new int[3];
1.5.2. 复杂类型
- String, Collection, List, ArrayList, Map, HashMap, TreeMap, Set, HashSet, TreeSet, ArrayDeque, Stack
- Class
1.5.3. 转换
1.6. 分配与释放
1.7. string
- String x="hello"; String x=new String("hello"); String x = new String(byte[]{})
- "hello"+"world"
- "Hello".charAt()
- "Hello".get_bytes() -> byte[]
- String::split() -> String []
- String.join(",", new String[] {"a"})
- String.valueOf(12);
- Integer.parseInt("12")
- String.format
1.8. iterator
1.9. array 与 List
- int [] x;
- 二维数组: int [][] x = new int[2][3]; int [][] x = {{1, 2}, {3, 4}};
- Arrays.asList(array) 转换为 List
- List.toArray(new Integer[0])
- array[0], array.length
- List.get(), List.set(), List.size(), List.isEmpty()
- List.subList
- List.add(), List.remove(), List.addAll()
- slice: List.subList, Arrays.copyOfRange
1.10. enum & match
1.11. 控制结构
- for (int =0; i<10; i++) {}
- for (int x; new int[]{1,2,3}) {}
- while, do while
1.12. 抽象数据类型
- Class Test {int x; int y;};
- Test x=new Test();
1.13. HashMap
- new HashMap<int,int>();
- get(k), containsKey(K)
- size(), isEmpty()
- put(K,V), remove(K)
- keySet(), values(), entrySet()
- for (Map.Entry entry:m.entrySet() { m.getKey(); m.getValue() }
1.14. Collections
- Collections.min(List), Collections.max(List), Collections.max(List, Comparator)
- Collections.reverse(List)
- Collections.sort(List)
- Collections.swap(List)
1.15. Arrays
- Arrays.sort
- Arrays.toString
- Arrays.copyOfRange
- Arrays.asList
1.16. 排序
- Arrays.sort(new int[]{3,2,1})
- List.sort(null)
- List.sort(new Comparator<Ineger> () { int compare(Integer x, Integer y) { return y-x; } }
- Collections.sort()
1.17. 最大堆
- PriorityQueue queue=new PriorityQueue()
- PriorityQueue queue=new PriorityQueue(new Comparator() {…})
1.18. math
1.19. random
1.20. package
- use std::collections::HashMap
- use util::*
