.Oracle a common function
length (x) returns the length of the X
converting lower (x) X lowercase
upper (x) X uppercase
substr (X, start [, length ]) Returns string X, starting from the start, intercept length characters, the default length, the default to the end of
the blank default assignment --nvl
SELECT NVL (field, 1) from table t
II. Various types of conversion
1.Map turn String
String name = String.valueOf(map.get("name"));
Map turn int
int age = Integer.valueOf("12");
2.map turn Integer
Numbers.IntegerOf(map2.get("yf"))
3.int turn String
1.String str = Integer.toString(i);
2.String s = String.valueOf(i);
3.String s = "" + i;
4.String turn int
int i = Integer.valueOf(str).intValue();
Three: equals () and ==, except that equals compares the contents are equal, the comparison is == variable address reference equality.
1 package com.de.test; 2 3 public class StringA { 4 public static void main(String[] args){ 5 String s1 = "hello"; 6 String s2 = "hello"; 7 String s3 = new String("hello"); 8 String s4 = new String("hello"); 9 System.out.println("s1:" + s1); 10 System.out.println("s2:" + s2); 11 System.out.println("s3:" +S3); 12 is System.out.println ( "S4:" + S4); 13 is System.out.println ( "---------- ---------- Comparative contents are equal ----- " ); 14 System.out.println (s1.equals (S2)); 15 System.out.println (s2.equals (S3)); 16 System.out.println (s3.equals (S4 )); . 17 System.out.println ( "reference address equality comparison ---------- ---------------" ); 18 is System.out.println (== S1 S2); . 19 System.out.println (== S2 S3); 20 is System.out.println (== S3 S4); 21 is } 22 is }
Performing the above code produces the following results
. 1 S1: Hello 2 S2: Hello . 3 S3: Hello . 4 S4: Hello . 5 ---------- compare the contents are equal --------------- . 6 to true . 7 to true . 8 to true . 9 ---------- whether the addresses match, the comparison reference --------------- 10 to true . 11 to false 12 is to false
Address reprint https://www.cnblogs.com/yiyidajiaoya/p/8316883.html