Java String format() 方法及示例
在Java中, String format() 方法使用给定的语言环境、指定的格式字符串和参数返回一个格式化的字符串。我们可以使用这种方法连接字符串,同时我们可以格式化输出的连接字符串。
语法:有两种类型的字符串format()方法
public static String format(Locale loc, String form, Object... args)
public static String format(String form, Object... args)
范围:
- 要应用于 format() 方法的语言环境值
- 输出字符串的格式。
- 参数 指定格式字符串的参数数量。它可能为零或更多。
返回类型:格式化字符串。
抛出异常:
- 空指针异常: 如果格式为空。
- 非法格式异常: 如果指定的格式不合法或参数不足。
示例 1:
java
// Java program to demonstrate
// working of format() method
// Main class
class GFG {
// MAin driver method
public static void main(String args[])
{
// Custom input string to be formatted
String str = "GeeksforGeeks";
// Concatenation of two strings
String s = String.format("My Company name is %s", str);
// Output is given upto 8 decimal places
String str2 = String.format("My answer is %.8f", 47.65734);
// Here answer is supposed to be %15.8f" and
// "47.65734000" there are 15 spaces
String str3 = String.format("My answer is %15.8f",
47.65734);
// Print and display strings
System.out.println(s);
System.out.println(str2);
System.out.println(str3);
}
}
java
// Java program to demonstrate Concatenation of Arguments
// to the string using format() method
// Main class
class GFG {
// Main driver method
public static void main(String args[])
{
// Custom input string to be formatted
String str1 = "GFG";
String str2 = "GeeksforGeeks";
// %1$ represents first argument
// %2$ second argument
String str = String.format(
"My Company name"
+ " is: %1$s, %1$s and %2$s",
str1, str2);
// Print and display the formatted string
System.out.println(str);
}
}
java
// Java program to Illustrate Left Padding
// using format() method
// Main class
class GFG {
// Main driver method
public static void main(String args[])
{
// Custom integer number
int num = 7044;
// Output is 3 zero's("000") + "7044",
// in total 7 digits
String str = String.format("%07d", num);
// Print and display the formatted string
System.out.println(str);
}
}
输出
My Company name is GeeksforGeeks
My answer is 47.65734000
My answer is 47.65734000
示例 2:
Java
// Java program to demonstrate Concatenation of Arguments
// to the string using format() method
// Main class
class GFG {
// Main driver method
public static void main(String args[])
{
// Custom input string to be formatted
String str1 = "GFG";
String str2 = "GeeksforGeeks";
// %1$ represents first argument
// %2$ second argument
String str = String.format(
"My Company name"
+ " is: %1$s, %1$s and %2$s",
str1, str2);
// Print and display the formatted string
System.out.println(str);
}
}
输出:
My Company name is: GFG, GFG and GeeksforGeeks
示例 3:
Java
// Java program to Illustrate Left Padding
// using format() method
// Main class
class GFG {
// Main driver method
public static void main(String args[])
{
// Custom integer number
int num = 7044;
// Output is 3 zero's("000") + "7044",
// in total 7 digits
String str = String.format("%07d", num);
// Print and display the formatted string
System.out.println(str);
}
}
输出:
0007044