Java Double parseDouble() 方法

2024 年 11 月 10 日 | 阅读 2 分钟

Java Double 类的 parseDouble 方法返回一个新创建的 double 值，该值初始化为由定义的 String 对应的取值。

此方法执行的操作与 Float 类的 valueOf() 方法相同。

语法

参数

s- 这是要解析的字符串。

返回值

parseDouble() 方法返回与传入参数对应的 double 值。

抛出

parseDouble() 方法抛出

1.NullPointerException- 如果传入的字符串为 null。

2.NumberFormatException- 如果传入的字符串不包含可解析的浮点数。

示例 1

public class Double_parseDoubleMethodExample1 {
    public static void main(String[] args) {
        String val1="1000";
        String val2="156";
        //here instead of adding it will concatenate two Strings
        //but will convert the String into Float
        Double d = Double.parseDouble(val1+val2);
        System.out.println("1. Sum ="+d);
        Double f1 = Double.parseDouble(val1)+Double.parseDouble(val2);
        System.out.println("2. Sum ="+f1);
        Double f2 = Double.parseDouble(val1)*Double.parseDouble(val2);
        System.out.println("3. Multiplication ="+f2);
        Double f3 = Double.parseDouble(val1)/Double.parseDouble(val2);
        System.out.println("4. Division ="+f3);
        Double f4 = Double.parseDouble(val1)%Double.parseDouble(val2);
        System.out.println("5. Reminder ="+f4);
    }
}

输出

1. Sum =1000156.0
2. Sum =1156.0
3. Multiplication =156000.0
4. Division =6.410256410256411
5. Reminder =64.0

示例 2

import java.util.Scanner;

public class Double_parseDoubleMethodExample2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter your age:");
        String str = scanner.next();
        //
        Double d1 = Double.parseDouble(str);
        Double d2 = 2018 - d1 ;
        System.out.println("Your year of birth is = "+d2);
        if(d2<1965){
            System.out.println("You are an adult, you are eligible for the discount in railway tickets.");
        }
        else{
            Double d3=d2-1965;
            System.err.println("Sorry! You are not eligible.Try again after "+d3+" years");
        }
    }
}

输出

Enter your age:09
Sorry! You are not eligible.Try again after 44.0 years
Your year of birth is = 2009.0

示例 3

import java.util.Scanner;

public class Double_parseDoubleMethodExample3 {
    public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
        System.out.print("Enter any string:");
        String str = scanner.next();
        Double d1= Double.parseDouble(str);
        System.out.println("Double value = "+ d1);

}
}

输出

Enter any string:Himanshu@123
Exception in thread "main" java.lang.NumberFormatException: For input string: "Himanshu@123"
	at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
	at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
	at java.lang.Double.parseDouble(Double.java:538)

示例 4

import java.util.Scanner;

public class Double_parseDoubleMethodExample4 {
    public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    try {
        System.out.print("Enter any string:");
        String str = scanner.next();
        Double d1 = Double.parseDouble(str);
        String str1="null";
        Double d2 = Double.parseDouble(str1);
        System.out.println("1. Double value = " + d1);
        System.out.println("2. Double value = " + d2);
    }catch (NullPointerException e){
        System.out.println("An exception "+e+" has occured.\nPlz enter a valid double integer");
    }catch (NumberFormatException ex){
        System.out.println("An exception "+ex+" has occured.\nPlz enter a valid double integer");
    }
  }
}

输出

Enter any string:himanshu@123
An exception java.lang.NumberFormatException: For input string: "himanshu@123" has occured.
Plz enter a valid double integer

下一主题Java-double-shortvalue-method

Java Double parseDouble() 方法

语法

参数

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抛出

示例 1

示例 2

示例 3

示例 4

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Java Double parseDouble() 方法

语法

参数

返回值

抛出

示例 1

示例 2

示例 3

示例 4

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