java常用api

1.Math.max()

2.數組長度 .length

3.字符串替換空格 str.replace(" “,”%20")

4.棧

import java.util.Stack;
Stack stack = new Stack();
stack.push
stack.pop()
stack.empty()

5.ArrayList

List<Integer> NumberList = new ArrayList<Integer>(Arrays.asList(2,4,1,3,5));
NumberList.remove(i);

6. 數組copy

Arrays.copyOfRange(pre, 1, i + 1)

7.判斷是否爲空

//數組
.length!=0
//ArrayList
.isEmpty()
//Stack
.size()!=0

8.新建一個二維數組

int [][] dp = new int[100][100];

9.字符串轉換字符數組

char[] chs1 = str1.toCharArray();
char[] chs2 = str2.toCharArray();

10.字符數組轉換字符串

char[] res = new char[dp[m][n]];
String.valueOf(res);